AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
200 PM PDT WED APR 2 2008
.SYNOPSIS...
A WEAKENING PACIFIC STORM WILL MOVE DUE EAST ACROSS THE AREA LATE
THIS AFTERNOON THROUGH EARLY THURSDAY. GUSTY WINDS WILL PRECEDE THE
STORM OVER THE DESERT AREAS. PRECIPITATION AMOUNTS ARE EXPECTED TO
BE LIGHT TO MODERATE...WITH THE SNOW LEVEL LOWERING TO AROUND 6000
FEET. FAIR...DRY...AND WARMER FOR FRIDAY AND SATURDAY. ANOTHER
TROUGH OF LOW PRESSURE WILL BRING A COOLING TREND FOR SUNDAY THROUGH
NEXT WEEK WITH ANOTHER CHANCE OF RAIN MONDAY NIGHT AND TUESDAY.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
BASED ON SATELLITE LOOP SINCE THIS MORNING...THE FORWARD SPEED OF
THE LOW APPEARS TO HAVE SLOWED...CLOSER TO 20 MPH. THE FIRST
RAINBAND HAS ALREADY PUSHED NORTH ACROSS SANTA BARBARA AND SAN LUIS
OBISPO COUNTIES AND FALLEN APART. A SECOND RAIN BAND WAS APPROACHING
THE OUTER ISLANDS AT 1300 PDT. THE LOW IS CUTOFF AND FILLING DUE
TO THE UPSTREAM RIDGE KICKED UP BY THE LOWS IN THE VICINITY OF
35N/148W AND 54N/1492W AT 1300 PDT/2000. BOUNDARY ISSUES AND
UNDERFORECASTING BY NAM12 MODEL IN EARLIER RUNS LED TO DISCOUNTING
THIS MODELS SOLUTION AMD RELIANCE ON THE HIGH RESOLUTION ECMWF/GFS40
MODELS FOR STRENGTH AND TIMING OF THIS EVENT. NEVERTHELESS ALL
MODELS TRACK THE COLD CORE OF THE SYSTEM...-24 DEGREES AT 500 MB AND
-5 DEGREES AT 700 MB DIRECTLY EAST ACROSS THE SOUTHERN CALIFORNIA
BIGHT AND ORANGE AND RIVERSIDE COUNTIES. BACK PEDALED A LITTLE MORE
ON QPF AMOUNTS THAN PREVIOUS SHIFT AND NEXT SHIFT MAY NEED TO RETARD
ONSET AND LOWER AMOUNTS EVEN MORE. A QUICK LOOK AT THE 18Z NAM MODEL
...EVEN THOUGH DISCOUNTED...SHOWS PRECIPITATION NOT ARRIVING IN THE
FORECAST AREA UNTIL AFTER 1100 PM/0600 UTC. BASED ON GFS40 MODEL
SHOWING CAPE VALUES AROUND 250 J/KG AND LIFTED INDICES -1...WHICH
THOUGH MARGINAL WAS TWICE AS STRONG AS EARLIER GUIDANCE...ADDED
SLIGHT CHANCE OF THUNDERSTORMS INTO FORECASTS FOR OUTER WATERS THIS
EVENING AND FOR ALL COASTAL WATERS/ORANGE COUNTY/RIVERSIDE
COUNTY/SAN DIEGO COUNTY ZONES BETWEEN 1100 PM-500 AM. FOR FRIDAY A
LOW MOVING INTO THE WASHINGTON/OREGON COASTS...CURRENTLY DEVELOPING
OVER THE GULF OF ALASKA...KNOCKS DOWN THE RIDGE. THE NEAR ZONAL
FLOWING IT ACROSS THE NORTH PACIFIC KEEPS THE RIDGE FROM REBUILDING
THROUGH THE WEEKEND. THOUGH A LOW AMPLITUDE RIDGE WILL STILL IN
PLACE OVER SOUTHWEST CALIFORNIA ON SATURDAY AND SUNDAY MODIFIED HIGH
AND LOW TEMPERATURES A FEW DEGREES EITHER WAY. AS NEXT WEEK UNFOLDS
THE ECMWF AND GFS MODELS NOW SHOW ANOTHER AND MUCH DEEPER LOW COMING
OUT OF THE GULF OF ALASKA ON TUESDAY AND MOVING INTO THE GREAT BASIN
BY WEDNESDAY. THE CURRENT FORECAST OF PRECIPITATION FOR MONDAY
NIGHT/TUESDAY WAS BASED ON THE 06Z DGEX MODEL WHICH SHOWED A 560 MB
TROUGH AT 500 MB MOVING ACROSS SOUTHWEST CALIFORNIA. NEITHER OF
THESE OTHER MODELS SHOW THIS NOW. LEFT THE GRIDS ESSENTIALLY
UNCHANGED FOR NOW.
&&
.AVIATION...
021900Z...LATEST MDCRS SOUNDINGS CONTINUE TO SHOW THE MARINE LAYER
DEPTH TO BE AROUND 3000 FEET. STRATUS HAS CLEARED OUT OF MOST AREAS
BUT CONTINUES TO HANG IN THE SAN BERNARDINO VALLEY AREA NEAR KONT.
EXPECT THIS AREA TO SCATTER OUT WITHIN THE NEXT HOUR OR TWO. CLOUDS
ASSOCIATED WITH THE COLD FRONT APPROACHING FROM THE WEST SHOULD
BEGIN TO SPREAD OVER THE AREA THIS AFTERNOON. EXPECT FRONTAL PASSAGE
TO OCCUR BETWEEN 06Z AND 12Z TONIGHT. LIGHT RAIN SHOULD BEGIN OVER
THE AREA AFTER SUNSET AND CONTINUE THROUGH THE NIGHT. CLOUD BASES
SHOULD LOWER TO BETWEEN 1500 AND 2500 FEET MSL WITH THE FRONT WITH
VISIBILITIES TO 2 MILES OR LESS AT TIMES IN SHOWERS. CLOUDS SHOULD
BEGIN TO BREAK UP DURING THE LATE MORNING TO EARLY AFTERNOON ON
THURSDAY. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 11 PM PDT THIS EVENING
FOR COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS.
PZ...NONE.
&&
$$
PUBLIC...BALFOUR
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
940 AM PDT WED APR 2 2008
.SYNOPSIS...
A WEAKENING PACIFIC STORM WILL MOVE DUE EAST ACROSS THE AREA LATE
THIS AFTERNOON THROUGH EARLY THURSDAY. GUSTY WINDS WILL PRECEDE THE
STORM OVER THE DESERT AREAS. PRECIPITATION AMOUNTS ARE EXPECTED TO
BE LIGHT TO MODERATE...WITH THE SNOW LEVEL LOWERING TO AROUND 6000
FEET. FAIR...DRY...AND WARMER FOR FRIDAY AND SATURDAY. ANOTHER
TROUGH OF LOW PRESSURE WILL BRING A COOLING TREND FOR SUNDAY THROUGH
EARLY NEXT WEEK WITH ANOTHER CHANCE OF RAIN MONDAY NIGHT AND TUESDAY.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THE CENTER OF THE CUTOFF LOW HAS BEEN TRACKING ALMOST DUE EAST FOR
THE PAST 18 HOURS NEAR 25 MPH. HEIGHT FALLS SUPPORT THIS TRACK
CONTINUED FOR AT LEAST ANOTHER 12 HOURS. THE LEADING EDGE OF
PRECIPITATION BAND IS CURRENTLY MOVING ACROSS THE POINT CONCEPTION
AREA. SEE AVIATION SECTION FOR EXTRAPOLATION TIMING ON IT REACHING
FORECAST AREA TODAY. QPF AMOUNTS WERE BACKED OFF FROM YESTERDAYS
FORECAST AND THIS APPEARS CORRECT. THE UPSTREAM LOWS IN THE VICINITY
OF 35N/150W AND 55N/152W AT 0800 PDT/1500 UTC HAVE KICKED UP A RIDGE
AHEAD OF THEM THAT ARE CAUSING THE LOW TO FILL AND WEAKEN AS IT
APPROACHES THE COAST. HOWEVER EVEN THOUGH A WEAKER SYSTEM IS
FORECAST TO MOVE ACROSS THE AREA THIS AFTERNOON THROUGH
THURSDAY...THE NAM MODEL STILL APPEARS TOO DRY AND CHECKING THIS
MODELS FORECAST AGAINST AVAILABLE OBSERVATIONS NEAR THE LOW AND THE
OTHER MODELS SHOWS THAT IT IS WARMER ON THE CORE TEMPERATURES AND
HIGHER ON THE SURFACE PRESSURES. THIS MIGHT BE DUE TO BOUNDARY ISSUE
PROBLEMS FROM EARLIER RUNS FEEDING INTO THE FIRST GUESS FIELD. THE
18Z RUN WILL NOT ARRIVE IN TIME TO INCORPORATE INTO THE AFTERNON
FORECAST PACKAGE...SO RELYING ON THE HIGH RESOLUTION ECMWF/GFS40
MODELS FOR THIS EVENT. OF THESE TWO MODELS THE FIRST GUESS FIELD OF
THE ECMWF WAS THE CLOSET TO THE OBSERVATIONS. THE COLD CORE OF THE
SYSTEM...-24 DEGREES AT 500 MB AND -5 DEGREES AT 700 MB SHOULD TRACK
DIRECTLY EAST ACROSS THE SOUTHERN CALIFORNIA BIGHT LATE THIS EVENING
AND ACROSS ORANGE AND RIVERSIDE COUNTIES LATE TONIGHT/EARLY THURSDAY
MORNING. CAPE VALUES FORECAST BY RECENTLY RECEIVED 12Z GFS40 MODEL
ARE NOW AROUND 250 J/KG AND LIFTED INDICES -1. THIS NUMBERS ARE
ABOUT TWICE AS STRONG AS EARLIER GUIDANCE AND SUGGEST MORE
INSTABILITY WITH THE POSSIBILTY OF ISOLATED LIGHTNING. WILL PROBABLY
ADD SLIGHT CHANCE OF THUNDERSTORMS BACK INTO FORECASTS FOR COASTAL
WATERS AND ZONES WEST OF THE MOUNTAINS FOR THESE PERIODS. OTHERWISE
PLANNING ON MINOR TWEAKS AND NO MAJOR CHANGES TO EXISTING
GRIDS/FORECASTS THROUGH THURSDAY. FOR FRIDAY A LOW MOVING INTO THE
WASHINGTON/OREGON COASTS...CURRENTLY IN THE VICINITY OF
55N/152W...KNOCKS DOWN THE RIDGE AND NEAR ZONAL FLOW FOLLOWING IT
ACROSS THE NORTH PACIFIC KEEPS THE RIDGE FROM REBUILDING THROUGH THE
WEEKEND. SO THOUGH A LOW AMPLITUDE RIDGE WILL STILL IN PLACE OVER
SOUTHWEST CALIFORNIA ON SATURDAY IT LOOKS LIKE AN ADJUST UPWARD IN
CLOUD COVER UPWARD AND SOME MODIFICATION OF TEMPERATURES WILL BE
NEEDED FOR SATURDAYS WEATHER. HAVE NOT FULLY EVALUATED MECHANISMS
SUPPORTING FORECAST OF PRECIPITATION FOR MONDAY NIGHT/TUESDAY BUT
NOT PLANNING ON MAKING ANY CHANGES AT THIS TIME.
&&
.AVIATION...
021456Z...MDCRS SOUNDINGS AND TOP REPORTS INDICATE THE MARINE LAYER
DEPTH WAS AROUND 3000 FEET THIS MORNING. STRATUS EXTENDS INLAND TO
THE LOWER SLOPES. NOT EXPECTING MUCH BREAKUP OF THE STRATUS TODAY.
THE LEADING EDGE OF CLOUDS ASSOCIATED WITH A COLD FRONT APPROACHING
SOUTHERN CALIFORNIA FROM THE WEST SHOULD REACH ORANGE COUNTY NEAR
KSNA BETWEEN 18Z AND 19Z TODAY THEN SPREAD EAST AND SOUTHEAST
THROUGH THE AREA THROUGH THE AFTERNOON. THE MAIN FRONT IS EXPECTED
TO MOVE THROUGH THE AREA TONIGHT. THE MAIN FRONTAL PASSAGE SHOULD
OCCUR BETWEEN 06Z AND 12Z TONIGHT. BASES SHOULD LOWER TO BETWEEN
1500 AND 2500 FEET MSL WITH THE FRONT WITH VISIBILITIES DOWN TO 2
MILES AT TIMES IN SHOWERS. EXPECT SOME BREAK UP OF THE CLOUDS BY
THURSDAY AFTERNOON. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 11 PM PDT THIS EVENING
FOR COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS.
PZ...NONE.
&&
$$
PUBLIC...BALFOUR
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
1131 AM EDT TUE APR 1 2008
.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL TRACK WELL TO OUR NORTH LATER THIS
AFTERNOON AND TONIGHT, PULLING A COLD FRONT ACROSS OUR AREA THIS
EVENING. HIGH PRESSURE WILL THEN BUILD OVER THE REGION ON
WEDNESDAY AND MOVE OFFSHORE LATER THURSDAY. AN AREA OF LOW
PRESSURE WILL THEN APPROACH FROM THE SOUTHWEST ON FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
OUR ENTIRE CWA REMAINS IN THE WARM SECTOR AS SOUTHERLY SURFACE
WINDS HAVE TURNED GUSTY AT TIMES. A SURFACE ANALYSIS PLACES A
STRENGTHENING LOW PRESSURE SYSTEM NORTH OF LAKE HURON WITH A
TRAILING COLD FRONT SOUTHWARD INTO THE OHIO VALLEY. THIS FRONT
WILL CONTINUE TO MOVE EASTWARD THROUGH THE AFTERNOON EVENTUALLY
ARRIVING INTO OUR AREA.
EMBEDDED WEAK AND SUBTLE SHORT WAVES HAVE GENERATED ROUNDS OF
SHOWERS SO FAR. THE MAIN BATCH OF SHOWERS CONTINUES TO MOVE ACROSS
EASTERN NEW JERSEY AND WILL EXIT THE AREA DURING THE EARLY
AFTERNOON. MEANWHILE, SOME ADDITIONAL SHOWER DEVELOPMENT HAS
POPPED UP ACROSS EASTERN PENNSYLVANIA. AS A RESULT, WE WILL RUN
WITH HIGH CHC POPS TO INDICATE A MORE SCATTERED COVERAGE TO THE
SHOWERS. THE VISIBLE SATELLITE IMAGERY SHOWS CLOUDS THINNING OUT
SOME ACROSS NORTHERN VIRGINIA TO WESTERN MARYLAND. THIS IS
TRACKING EASTWARD, HOWEVER THERE REMAINS AN ABUNDANCE OF MOISTURE
ACROSS OUR AREA. THERE STILL CAN BE SOME BREAKS IN THE CLOUDS
ESPECIALLY ACROSS SOUTHEASTERN PENNSYLVANIA ON SOUTHWARD, HOWEVER
CONFIDENCE IS NOT HIGH REGARDING THIS. IF MORE BREAKS OCCUR, THEN
TEMPERATURES WILL LIKELY SPIKE UP MORE THAN CURRENTLY THINKING.
WE EDGED THE HIGH TEMPERATURES UP ACROSS MOST OF THE AREA JUST A
BIT BASED ON TRENDS AND THE POTENTIAL FOR A FEW BREAKS IN THE
CLOUDINESS. THE IMMEDIATE COAST IS A BIT TRICKY AS SURFACE WINDS
ARE SOUTHERLY WITH THE TRAJECTORY OFF THE WATER FOR MOST OF
COASTAL LOCALES. THE SURFACE WINDS MAY VEER A BIT MORE TO THE
SOUTHWEST, HOWEVER MANY COASTAL LOCATIONS ARE RIGHT AROUND 50
DEGREES ATTM. THEREFORE WE OPTED TO LOWER THE HIGHS THERE SOME.
SOME AIRCRAFT SOUNDINGS FROM PHILADELPHIA INTERNATIONAL ALONG WITH
NEARBY 12Z RAOBS INDICATE SOME 50 KNOT WINDS AROUND 2500 FEET.
THIS LOW-LEVEL JET IS FORECAST TO GRADUALLY SLIDE EASTWARD THROUGH
THE AFTERNOON HOWEVER STILL A DECENT WIND FIELD IS PRESENT. WHILE
SURFACE BASED INSTABILITY IS NOT EXISTENT THUS FAR, FORECAST
SOUNDINGS DO INDICATE SOME WEAK INSTABILITY THROUGH THE AFTERNOON.
THIS SETUP IS BASICALLY OF LOW CAPE /ON THE BASIS OF NOT MUCH
BREAKS IN THE CLOUDS/ WITH A STRONG WIND FIELD. AS A RESULT, WE
EXPANDED THE MENTION OF A CHC OF SOME THUNDERSTORMS ACROSS THE
ENTIRE AREA, WHICH MATCHES UP WITH SPC`S DAY ONE OUTLOOK. THUNDER
MAY NOT OCCUR UNTIL LATER THIS AFTERNOON OR EARLY THIS EVENING AS
THE FRONTAL SURFACE NEARS AND MOVES THROUGH. THERE IS THE CHC OF
SOME LOW-TOPPED CONVECTIVE ELEMENTS THAT MAY CONTAIN LITTLE OR NO
LIGHTNING. WITH THE STRONGER WINDS PRESENT, SOME OF THOSE CELLS
COULD TRANSPORT THAT WIND DOWN TO THE SURFACE. WE CARRIED A MENTION
OF THIS POTENTIAL IN THE HAZARDOUS WEATHER OUTLOOK /HWO/.
ALL THE HOURLY GRIDS WERE UPDATED TO REFLECT THE LATEST CONDITIONS
AND EXPECTED TRENDS THROUGH THE AFTERNOON. WE BUMPED UP THE WINDS
SOME AS WELL THROUGH THE AFTERNOON GIVEN THE TIGHTENING PRESSURE
GRADIENT AND WITH ADDED VERTICAL MIXING.
AS THE AREA OF LOW PRESSURE TRACKS WELL TO OUR NORTH TONIGHT, THE
COLDEST AIR WILL REMAIN NORTH OF OUR CWA BUT WE WILL HAVE A FEW
HOURS OF POSSIBLY STRONG GUSTS ESPECIALLY AFTER MIDNIGHT. WINDS
MAY GUST TO 40 MPH WITH AND JUST BEHIND THE FRONT. WITH THE UPPER
FLOW STRONGEST OVER OUR NORTHERN ZONES, THE SURFACE FRONT AND
CLOUDS WILL CLEAR THE NORTHERN ZONES BUT TAKE A FEW HOURS LONGER
IN THE SOUTH. WITH THAT, THE TEMPERATURES WILL PLUNGE DOWN INTO
THE MID 20S NORTHERN AREAS AND STILL BE IN THE MID 40S BY DAYBREAK
SOUTH.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
RATHER QUIET PERIOD AS HIGH PRESSURE SLIDES EAST WEDNESDAY INTO
THURSDAY WITH CLEAR SKIES BUT MUCH COOLER TEMPERATURES IN THE 40S
AND 50S. WEDNESDAY NIGHT LOWS DOWN INTO THE UPPER TEENS NORTH TO THE
FREEZING MARK SOUTHERN AREAS AND HIGHS ON THURSDAY IN THE 50S WITH
THE EXCEPTION OF THE 40S FAR NORTH.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
THERE IS CONSIDERABLE MODEL DIVERSITY FOR THIS FORECAST PACKAGE AND
THEREFORE WE HAVE VERY LOW CONFIDENCE IN THE OUTCOME. THE 00Z ECMWF
IS CONSIDERABLY DIFFERENT FROM THE 12Z GFS/UKMET/GLOBAL CANADIAN.
WITH EDT IN EFFECT IT MAKES IT HARD TO SEE WHAT THE ECMWF WILL DO
NEXT. PERHAPS THE NEXT SHIFT WILL HAVE THE OPPORTUNITY TO SEE SOME
BETTER BALANCE BETWEEN THE MODELS.
LATE THURSDAY BEGINS THE NEXT ROUND OF SEVERAL DAYS WITH
PRECIPITATION IN THE FORECAST. THE PRECIPITATION WILL BE PRIMARILY
RAIN HOWEVER THERE REMAINS THE POSSIBILITY FOR A MIXED BAG AS YOU
HEAD NORTH THROUGH THE CWA. HIGH PRESSURE OVER THE REGION WILL
MOVE OFFSHORE THURSDAY AS LOW PRESSURE DEVELOPS OVER THE SOUTHERN
PLAINS AND MOVES EASTWARD. BY 12Z FRIDAY THIS LOW IS FORECAST TO
BE OVER THE OHIO VALLEY. THIS IS SEEN IN GFS/UKMET AND CANADIAN.
THE ECMWF HAS THIS FEATURE OVER THE SOUTHERN PLAINS BY 12Z FRIDAY.
AS THE LOW MOVES EASTWARD IT IS FORECAST TO INTENSIFY. A WARM
FRONT WILL CROSS THE REGION BY FRIDAY EVENING WITH THE COLD FRONT
MOVING THROUGH FRIDAY NIGHT. THE MODELS DO DIFFER AS TO WHERE TH
LOW WILL END UP BY 00Z SATURDAY BUT THE CONSENSUS SEEMS TO BE AS
FAR WEST AS WESTERN NEW YORK OR AS FAR EAST AS NORTHEASTERN
PENNSYLVANIA. THE LOW EVENTUALLY MOVES OFF TO THE NORTHEAST AND IS
OVER THE CANADIAN MARITIMES BY 12Z SATURDAY.
WE MAY SEE SOME DRY SPOTS OVER THE EARLY PART OF THE WEEKEND BUT
WITH THE HIGH UNCERTAINTY OF THIS FORECAST WE HAVE DECIDED TO LEAVE
SCHC POPS IN ACROSS THE REGION.
WEAK HIGH PRESSURE BUILDS IN SATURDAY AS A POSSIBLE LOW PRESSURE
SYSTEM BEGINS TO MOVE UP THE EASTERN SEABOARD SATURDAY NIGHT. THE
PERIOD ENDS WITH HIGH PRESSURE BUILDING IN FROM THE WEST.
HPC AND GFS MOS GUIDANCE DIFFERED QUITE A BIT WHEN IT CAME TO
TEMPERATURES WITH THE GMOS MUCH COLDER IN THE NORTHERN HALF OF THE
CWA FOR MAJORITY OF THE EXTENDED. THEREFORE, STUCK WITH HPC
THROUGHOUT THE ENTIRE PERIOD /WITH SOME MINOR ADJUSTMENTS/ IN ORDER
TO KEEP A BETTER CONTINUITY WITH THE PREVIOUS FORECAST.
&&
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
DESPITE ALL THE TERMINALS IN THE WARM SECTOR, PLENTY OF LOW CLOUDS
PERSIST AS AN ABUNDANCE OF MOISTURE IS IN PLACE. VISIBLE SATELLITE
AND SURFACE OBSERVATIONS ACROSS NORTHERN VIRGINA TO WESTERN
MARYLAND INDICATE THAT THE CLOUDS HAVE THINNED OUT WITH CEILINGS
GREATLY IMPROVING. THIS IS EDGING EASTWARD, HOWEVER ADDITIONAL
SHOWERS ARE FORMING ACROSS EASTERN PENNSYLVANIA. THE LATEST
THINKING IS THAT SOME IMPROVEMENT WILL OCCUR BY LATER THIS
AFTERNOON, PROBABLY TO AROUND MARGINAL VFR. TERMINALS SEEING THIS
OCCUR WILL PROBABLY BE ONES THAT ARE FARTHER TO THE SOUTH. IT
SHOULD BE NOTED THAT ANY IMPROVEMENT IN CEILINGS CARRIES LOWER
CONFIDENCE ATTM. WE WILL CONTINUE TO ISSUE AMENDMENTS TO REFLECT
THE LATEST THINKING. SOME THUNDER IS STILL POSSIBLE MAINLY LATER
THIS AFTERNOON AND EARLY EVENING, AND WE WILL TRANSITION TO A
TEMPO GROUP WITH A CB DESCRIPTOR TO INDICATE THIS POSSIBILITY. THE
SOUTHERLY FLOW HAS INCREASED ACROSS ALL AREAS AND WILL CONTINUE.
PLENTY OF WIND ENERGY ABOVE THE SURFACE, THEREFORE SOME LOW-LEVEL
WIND SHEAR WILL BE AROUND DESPITE THE STRONGER WINDS GRADUALLY
SLIDING TO THE EAST LATER THIS AFTERNOON.
AFTER FRONTAL PASSAGE IN THE 00Z TO 02Z TIME FRAME FROM WEST TO
EAST, IMPROVING CONDITIONS /TO VFR/ SHOULD COMMENCE, WITH CLEARING
OCCURRING AFTER 03Z TO 05Z. WESTERLY WINDS VEERING TO WEST AND
NORTHWEST SHOULD BE RATHER GUSTY IN THE POST-FRONTAL ENVIRONMENT
IN THE EVENING AND INTO THE OVERNIGHT PERIOD.
OUTLOOK...
IT SHOULD REMAIN RATHER BREEZY INTO WEDNESDAY. HIGH PRESSURE AND DRY
CONDITIONS SHOULD FOLLOW FOR WEDNESDAY INTO EARLY THURSDAY. THE
CHANCE FOR RAIN AND LOWERING CONDITIONS RETURNS FROM LATE THURSDAY
INTO EARLY SATURDAY.
&&
.MARINE...
WINDS ARE GUSTING TO ABOUT 25 KNOTS AND AN EARLY REPORT FROM THE
CAPE MAY-LEWES FERRY INDICATED WINDS TO 25 KNOTS ALSO IN THE LOWER
DELAWARE BAY, THEREFORE THE SMALL CRAFT ADVISORY REMAINS IN
EFFECT. STABILITY FACTORS WILL PRECLUDE THE STRONGEST WINDS OFF
THE SURFACE FROM MIXING DOWNWARD UNTIL THE SURFACE FRONT MOVES
PAST THIS EVENING. SEAS ARE MORE THAN 5 FEET ON THE OCEAN, AND
LIKELY NEAR 5 FT AROUND THE MOUTH OF LOWER DELAWARE BAY, SO THE
EXISTING SMALL CRAFT ADVISORY WILL BE KEPT IN PLACE FOR THESE
LOCATIONS. THE TIME FOR THE UPPER BAY TO NEED AN ADVISORY, EARLIER
PLANNED TO DEVELOP BY 12Z, STILL LOOKS LIKE A GOOD TIME AND WILL
BE RETAINED. EVEN IF THAT IS AN HOUR OR A COUPLE OF HOURS EARLY,
THAT WILL ALLOW FOR SOME POSITIVE LEAD TIME FOR THE EXPECTED
CONDITIONS. OTHERWISE, SMALL CRAFT ADVISORY CONDITIONS WILL
CONTINUE THROUGH FRONTAL PASSAGE THIS EVENING. THEN, WITH
TURBULENT FLOW MIXING DOWN TO THE SURFACE, AND 925 HPA WINDS SHOWN
IN THE 35 TO 45 KNOT RANGE TONIGHT, A GALE WARNING WILL BE ISSUED
FOR EXPECTED GUSTS OF AROUND 35 KNOTS FROM 02Z TO 12Z WEDNESDAY.
POST-COLD FRONTAL NORTHWEST WINDS WILL BE BLUSTERY INTO WEDNESDAY,
BUT WILL DROP OFF WEDNESDAY AFTERNOON AND ALLOW CONDITIONS TO DROP
BELOW ADVISORY CRITERIA AS HIGH PRESSURE MOVES BACK IN. THE HIGH
WILL INFLUENCE OUR WEATHER THROUGH THURSDAY. ANOTHER LOW MOVING UP
TO OUR WEST COULD BRING US ADVISORY CONDITIONS LATE THURSDAY INTO
FRIDAY.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ430-
431-450>455.
GALE WARNING FROM 10 PM THIS EVENING TO 8 AM EDT WEDNESDAY FOR
ANZ430-431-450>455.
&&
$$
SYNOPSIS...EBERWINE/GORSE
NEAR TERM...EBERWINE/GORSE
SHORT TERM...EBERWINE
LONG TERM...MEOLA
AVIATION.../ GORSE
MARINE.../ GORSE
AREA FORECAST DISCUSSION...UPDATE
NWS MARQUETTE MI
125 AM EDT TUE APR 1 2008
UPDATED FOR AVIATION
...LATE SEASON WINTER STORM MOVING INTO UPPER MICHIGAN WITH BLIZZARD
CONDITIONS POSSIBLE OVER THE NORTH CENTRAL TUE MORNING...
...TRAVEL STRONGLY DISCOURAGED THROUGH TUE MORNING...
.UPDATE...
ADDED MENTION OF ELEVATED TS TO SRN MNM COUNTY IN ADVANCE OF CLUSTER
OF CNVCTN MOVING NE THRU CNTRL WI WHERE 18Z NAM F6 SHOWS H7-5 LAPSE
RATES APRCHG 7C/KM JUST TO THE N OF H85 WARM FNT.
&&
.SYNOPSIS...
20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER
LEVEL TROUGHING OVER THE NORTHWEST U.S. INTO THE NRN PLAINS AND
STRONG RIDGING ALONG THE EAST COAST. WITHIN THE TROUGH...TWO MAIN
FEATURES ARE EVIDENT FOR THE WINTER STORM. FIRST IS A SHRTWV OVER
ERN NEBRASKA AND THE SECOND IS AN UPPER LEVEL LOW OVER RIVERTON WY.
DPVA AHEAD OF THE ERN NEBRASKA SHRTWV...STRONG WARM ADVECTION OF
MOISTURE INTO THE UPPER MIDWEST (PRECIPITABLE WATER VALUES NEAR 200
PCT OF NORMAL PER 12Z RAOBS)...AND UPPER DIVERGENCE IN THE RIGHT
ENTRANCE REGION OF A 130 KT JET STRETCHING FROM NE MN INTO NORTHERN
ONTARIO...HAS LED TO THE DEVELOPMENT OF A DEFORMATION ZONE OF MOSTLY
LIGHT TO MODERATE PCPN FROM CENTRAL/SRN MN THROUGH MUCH OF WI AND
NOW INTO THE WI BORDER AREAS. WITHIN THIS ZONE...THERE IS A POCKET
OF HEAVIER PCPN WHICH HAS BEEN WELL ADVERTISED NEAR WAUSUA MOVING
NE. SOME LIGHTNING HAS EVEN BEEN DETECTED WITHIN THIS HEAVIER PCPN.
RAIN/SNOW/SLEET LINE IS SITUATED FROM ROCHESTER MN TO JUST SOUTH OF
WAUSAU AND INTO SRN MENOMINEE COUNTY. RECENT CALLS HAVE FOUND RAIN
IN MENOMINEE AND ESCANABA. SURFACE LOW ASSOCIATED WITH ALL THIS PCPN
CURRENTLY NEAR INDIANOLA IA WITH A PRESSURE AROUND 999MB. COMPARISON
WITH MODEL DATA APPEARS THAT THE NAM MAY BE DOING A BETTER JOB WITH
THE STRENGTH COMPARED TO THE GFS. TO THE NORTHWEST...1030MB HIGH
PRESSURE IS SITUTATED OVER MANITOBA. 850MB TEMPS ARE SOMEWHAT COLD
AHEAD OF THIS HIGH...WITH 12Z RAOBS SHOWING -7C AT INL AND -10C AT
CWPL...SO THERE IS SOME COLDER AIR TO FILTER INTO THE AREA. OVER THE
CWA...SNOW HELD OFF FOR MUCH OF THE MORNING AND EARLY AFTERNOON DUE
TO DRY AIR IN THE 700-900MB LAYER AS SEEN ON TAMDAR SOUNDINGS
(DEWPOINT DEPRESSIONS AROUND 10C).
&&
.SHORT TERM (TONIGHT AND TUE)...
MODELS ARE NOW IN GOOD AGREEMENT WITH REGARDS TO THE TRACK OF THE
LOW PRESSURE SYSTEM AS IT LIFTS ACROSS NORTHERN LAKE HURON TUE
MORNING. AFTER NOTICING THAT THE GFS IS A BIT TOO WEAK WITH THE
SYSTEM CURRENTLY FOR ONLY A 6 HOUR FORECAST...HAVE FOLLOWED A BIT
CLOSER THE 12Z NAM/LOCAL WRF-ARW/RUC 13 MODELS WHICH ARE SLIGHTLY
DEEPER. SHOULD NOTE THAT THE NEW 18Z NAM LOOKS EVEN BETTER WITH THE
CURRENT STRENGTH...AND DISPLAYS EVEN MORE PCPN FOR THE CWA THAN THE
GOING FORECAST.
DETAILS...SHRTWV OVER ERN NEBRASKA WILL CONTINUE LIFTING NORTHEAST
TONIGHT. HOWEVER...THE UPPER LOW OVER WYOMING IS PROGGED TO CATCH UP
WITH THIS SHRTWV...RESULTING IN A PHASING OF THE TWO FEATURES
BASICALLY OVER THE CWA AROUND 12Z. THIS PHASING WILL CAUSE THE LOW
TO DEEPEN MORE AFTER 06Z...TO SOMEWHERE AROUND 993MB OVER NRN LK
HURON BY 12Z TUE. UNTIL THE PHASING OCCURS...THERE ARE TWO PERIODS
OF CONCERN. FOR LATE THIS AFTERNOON AND EVENING...DEFORMATION ZONE
WILL ENVELOP MUCH OF UPPER MICHIGAN BY 22Z AS THE STRONG 700-600MB
FRONTOGENESIS ZONE AND UPPER JET SHIFT EAST. AREA OF HVY PCPN LIKELY
TO GO ACROSS THE SOUTH CENTRAL U.P.. A REPORT OF AN INCH PER HOUR
CAME IN FROM MARSHFIELD AND 2 INCHES PER HOUR IN WAUSAU...AND THIS
SHOULD EASILY OCCUR IN NORTHERN MENOMINEE COUNTY WHERE SOUNDING
PROFILES ARE SHOWN TO STAY SOLIDLY BELOW FREEZING. IN SRN MENOMINEE
COUNTY AND OTHER AREAS ALONG LAKE MICHIGAN UP INTO LUCE COUNTY...
SOUNDINGS ARE A LITTLE LESS CERTAIN...WITH SNOW...SLEET OR RAIN ALL
POSSIBLE. THERE WAS A REPORT OF SLEET ACCUMULATING ON THE GROUND AT
WAUSAU...SO WOULD NOT BE SURPRISED TO SEE THE SAME IN SRN MENOMINEE
COUNTY. OVER THE REST OF THE CWA...SNOWFALL ACCUMULATION RATES OF
ONE HALF OF AN INCH TO AN INCH PER HOUR SEEM LIKELY UNDER THE
DEFORMATION ZONE. THUS...GOING WARNINGS LOOK FINE. AFTER
MIDNIGHT...THE UPPER JET FORCING EXITS...BUT THE PHASING BEGINS TO
OCCUR. PV AND THETA-E PLOTS ACTUALLY SUGGEST THE DEVELOPMENT OF THE
FULL-FLEDGED TROWAL TOWARDS LATE IN THE NIGHT...WHICH SHOULD HELP
KEEP SOME LIGHT TO MODERATE BANDED PCPN GOING OVER THE CWA. COMBINE
THIS WITH COLD ADVECTION ON THE BACK SIDE OF THE LOW AND A GOOD
SETUP IS IN PLACE FOR LAKE ENHANCEMENT/UPSLOPE. WITH WINDS OUT OF
THE NORTH TO NORTHEAST...AND STRONG AT THAT (900MB WINDS PROGGED AT
50 KT BY 12Z)...UPSLOPE SHOULD BE REALLY STRONG OVER THE HIGHER
TERRAIN OF THE FAR WEST AND NORTH CENTRAL. TIMING OF THE BEST
SNOW...BASED ON 900MB TEMPS THAT CORRELATED WELL WITH THE APRIL 4
2007 BLIZZARD (AROUND -8C TO START UPSLOPE) SUGGESTS BETWEEN 06-09Z
OUT WEST AND 09-12Z OVER THE NORTH CENTRAL. WOULD NOT BE SURPRISED
TO SEE INCH PER HOUR RATES... ESPECIALLY SINCE THE SNOW TO WATER
RATIOS WILL BE HIGHER THANKS TO THE COLDER AIR. MAY HAVE TO WATCH
FOR POTENTIAL FOR WINDS REACHING HIGH WIND WARNING CRITERIA TUE
MORNING IN THE NORTH CENTRAL AS WELL...ESPEICALLY IF THE 18Z NAM
PANS OUT. PCPN WILL DIMINISH WEST TO EAST ON TUE AS THE PHASED UPPER
TROUGH MOVES AWAY FROM THE CWA...ALLOWING DRIER AIR AND SUBSIDENCE
TO MOVE IN.
QPF AMOUNTS FOLLOW A BLEND OF THE 12Z NAM...REGIONAL CANADIAN AND
LOCAL WRF-ARW. NEW 18Z NAM IS EVEN HEAVIER WITH THE QPF...WHICH
MIGHT NOT BE OUT OF THE QUESTION WITH THE SNOW REALLY INTENSIFYING
OVER THE MINNEAPOLIS AREA. THE UPSLOPE IS VERY IMPRESSIVE OFF THE
18Z NAM AS WELL (TOTAL QPF OF 2.24 INCHES AT OUR OFFICE).
TEMPS FOR TONIGHT AND TOMORROW LOOK REASONABLE AND VERY LITTLE
MODIFICATION MADE.
.LONG TERM... (TUE NIGHT THRU MON)
QUIET NIGHT EXPECTED TUE NIGHT AS SFC HIGH PRES MOVES FROM THE UPPER
MISSISSIPPI VALLEY INTO THE GREAT LAKES REGION. IT WILL NOT BE AN
IDEAL RADIATIONAL COOLING SETUP WITH CENTER OF SFC HIGH PASSING THRU
SRN WI. IN ADDITION...THERE IS SOME UNCERTAINTY ON THE CLOUD
SITUATION AS STRONGER WAA PATTERN TO THE NW SHOULD SEND SOME CLOUDS
SE INTO UPPER MI. NONETHELESS...FRESH SNOW COVER/LIGHT WINDS AND AT
LEAST SOME TIME WITH LIMITED CLOUD COVER SUGGEST GOING BLO MOS
GUIDANCE AS PREVIOUS FCST HAD INDICATED. SHOULD THE NIGHT END UP
MOSTLY CLEAR...TEMPS MAY SLIP BLO ZERO IN THE TYPICAL COLD SPOTS.
A COUPLE OF WEAK SHORTWAVES WILL BE TRACKING THRU THE UPPER GREAT
LAKES REGION WED. SINCE BEST ISENTROPIC ASCENT SLIDES BY JUST N OF
UPPER MI AND THERE WILL BE A DRY AIRMASS TO OVERCOME INITIALLY...
OPTED TO MAINTAIN A DRY FCST WED WITH THE EXCEPTION OF NRN LAKE
SUPERIOR.
NEXT SHORTWAVE TROF SWINGS THRU THE UPPER LAKES ON THU. SINCE
ANTECEDENT AIRMASS WON`T BE AS DRY AS WED...ISENTROPIC ASCENT MAY BE
SUFFICIENT FOR SOME -SN WITH THIS SYSTEM LATE WED NIGHT THRU THU
MORNING. HAVE THUS RETAINED SLIGHT CHC POPS FOR -SN AS SHORTWAVE
PASSES.
FRI THRU MON...ALTHOUGH THERE ARE SIGNIFICANT MODEL DIFFERENCES WITH
THE PATTERN ACROSS THE CONUS...IT APPEARS AT THE MOMENT THAT THIS
SHOULD BE A RELATIVELY QUIET PERIOD OF WEATHER ACROSS THE FCST AREA.
THE ECMWF DEVELOPS MUCH MORE TROFFING OVER THE WRN CONUS OVER THE
WEEKEND INTO EARLY NEXT WEEK THAN THE GFS...RESULTING IN SW FLOW
TAKING SHAPE INTO THE GREAT LAKES. THE GFS HAS A W TO NW FLOW INTO
THE GREAT LAKES AS POLAR VORTEX OVER HUDSON BAY MAINTAINS INFLUENCE
OVER THE AREA. THE GLOBAL CANADIAN OFFERS A SOLUTION BTWN THE GFS
AND ECMWF. GIVEN THE DIFFERENCES...IT`S USUALLY BEST TO MAKE MINIMAL
CHANGES TO PREVIOUS FCST UNTIL BETTER MODEL AGREEMENT DEVELOPS. IN
THIS CASE...THE PREVIOUS FCST LINES UP REASONABLY WELL WITH THE
GFS...AND THE 12Z ECMWF HAS TRENDED SOMEWHAT TOWARD THE GFS
SOLUTION. SO...WILL MAINTAIN LOW POPS OVER THE WEEKEND FOR THE
POSSIBILITY OF A COLD FRONT SETTLING INTO THE UPPER LAKES EARLY SAT
AND THEN THE POTENTIAL FOR ANOTHER FROPA SUN. AIRMASS SHOULD BE WARM
ENOUGH TO FOR MIXED PTYPES (-SN/-RA) DURING THE AFTN HRS. EXPECT A
DRY DAY MON.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
EXPECT PREDOMINANT IFR/LIFR CONDITIONS TO PERSIST THRU SUNRISE WITH
INCRSG NNE WINDS CAUSING NEAR BLIZZARD CONDITIONS AT SAW ON TUE MRNG
AS LO PRES MOVES FM NR MKE TO SE ONTARIO THIS MRNG. CONDITIONS
SHOULD IMPROVE RPDLY TO VFR BY LATE TUE MRNG AT CMX AND THEN IN THE
AFTN AT SAW AS SFC LO PULLS TO THE NE AND DRIER AIR INVADES FM THE
W. HI PRES PUSHING INTO THE UPR MIDWEST/WEAKENING PRES GRADIENT WL
ALSO ALLOW WINDS TO DIMINISH QUICKLY BY LATE IN THE DAY.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
LOW PRESSURE OVER IOWA WILL DEEPEN TONIGHT AS IT LIFTS TO NORTHERN
LAKE HURON BY TUE MORNING. 35 KT GALE FORCE WINDS ARE EXPECTED TO
DEVELOP ACROSS LAKE SUPERIOR THIS EVENING...THEN INTENSIFY TO 40 TO
45 KT AFTER MIDNIGHT. IT IS POSSIBLE FOR STORM FORCE WINDS TO OCCUR
ON EASTERN LAKE SUPERIOR TOMORROW MORNING...BUT CONFIDENCE IS NOT
HIGH ENOUGH YET TO ISSUE THE STORM WARNING. WINDS WILL COME DOWN
FAIRLY QUICK TOMORROW AS THE LOW DEPARTS AND A HIGH PRESSURE RIDGE
BUILDS IN. BEYOND TUE NIGHT...WINDS LOOK TO REMAIN BELOW 25 KT
THROUGH THE REST OF THE FORECAST.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
WINTER STORM WARNING UNTIL 1 PM EDT /NOON CDT/ THIS AFTERNOON
FOR MIZ002-009-013-014-084.
WINTER STORM WARNING UNTIL 5 PM EDT THIS AFTERNOON FOR MIZ007-
085.
SNOW AND BLOWING SNOW ADVISORY UNTIL 1 PM EDT THIS AFTERNOON FOR
MIZ001-003.
BLIZZARD WARNING UNTIL 5 PM EDT THIS AFTERNOON FOR MIZ006.
WINTER STORM WARNING UNTIL 2 PM EDT THIS AFTERNOON FOR MIZ004.
BLIZZARD WARNING UNTIL 2 PM EDT THIS AFTERNOON FOR MIZ005.
WINTER STORM WARNING UNTIL 7 AM CDT THIS MORNING FOR MIZ010>012.
LAKE SUPERIOR...
GALE WARNING UNTIL 8 PM EDT THIS EVENING FOR LSZ265>267.
GALE WARNING UNTIL 2 PM EDT THIS AFTERNOON FOR LSZ244>249-264.
GALE WARNING UNTIL 11 AM EDT /10 AM CDT/ THIS MORNING FOR
LSZ240>243.
GALE WARNING UNTIL 2 AM EDT EARLY THIS MORNING FOR LSZ162.
GALE WARNING UNTIL 8 AM EDT THIS MORNING FOR LSZ263.
GALE WARNING UNTIL 6 PM EDT THIS AFTERNOON FOR LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 8 AM THIS MORNING TO 3 PM EDT THIS
AFTERNOON FOR LMZ221-248-250.
&&
$$
UPDATE...KC
SYNOPSIS/SHORT TERM...AJ
LONG TERM...ROLFSON
AVIATION...KC
MARINE...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
1023 AM CDT TUE APR 1 2008
.UPDATE...SHORT WAVE TROF THAT BROUGHT WIDESPREAD SNOWS TO THE SE
TWO THIRDS OF THE DLH CWA OVERNIGHT CONTINUES TO PULL AWAY FROM
THE WRN GREAT LAKES REGION LATE THIS MORNING..WITH HEAVY SNOWS NOW
CONFINED TO THE EASTERN UPPER PENINSULA OF MICHIGAN. THERE MAY BE
A SHORT WINDOW OF OPPORTUNITY FOR A FEW LIGHT LAKE EFFECT SNOW
SHOWERS IN ASHLAND/IRON COUNTIES..BUT OVERALL LOW LEVEL FLOW WILL
BE WEAKENING/BACKING TO A MORE WESTERLY DIRECTION RATHER RAPIDLY
WITH TIME OVER THE NEXT FEW HOURS..AND THIS WILL BE CONCURRENT
WITH AN INJECTION OF DRIER AIR IN THE LOW LEVELS..SO OVERALL
CHANCES OF ANY ADDITIONAL PRECIPITATION ARE DECREASING FAST.
THE PRIMARY CONCERNS FOR THIS UPDATE ARE TEMPS/SKY COVER AND
WINDS/WAVES. NEW SNOW COVER WUD ARGUE FOR LOWERING TEMPS SOMEWHAT
OVER CENTRAL MN/NW WISCONSIN..BUT TEMPS DID NOT COOL TOO MUCH
OVERNIGHT AND ARE STARTING OUT IN THE MID-UPPER 20S. SO..WITH
WARM EARLY APRIL SUN..MID TO MAYBE EVEN UPPER 30S DONT SEEM A
STRETCH..ESPECIALLY WITH ONLY THIN HIGH LEVEL CLOUDS LINGERING IN
A FEW AREAS. WE HAVE ALSO DECREASED SKY COVER SIGNIFICANTLY FROM
THE PREVIOUS GRIDDED FORECAST BASED PRIMARILY ON LATEST SATELLITE
TRENDS..ALTHOUGH THERE WILL PROBABLY BE SOME CUMULUS FORMATION
THIS AFTERNOON. WINDS WILL ALSO RAPIDLY DECREASE CENTRAL AND EAST
THIS AFTERNOON AS LOW LEVEL RIDGING BUILDS IN AND GRADIENT WEAKENS
BY 21Z. WITH STEEP LOW LEVEL LAPSE RATES BY THIS AFTERNOON AND
APPROACHING WEAK S/W TROF OVER SRN MANITOBA..ITS NOT OUT OF THE
QUESTION THAT THERE COULD BE A FEW LIGHT SHOWERS IN THE FAR NW
ZONES..BUT CONFIDENCE IN THIS IS NOT HIGH ENUF TO PUT INTO THE
FORECAST ATTM. UPDATES TO ALL GRIDS/TEXT PRODUCTS TO REFLECT THE
AFOREMENTIONED THINKING ARE ALREADY AVAILABLE.
FINALLY..AS WINDS SUBSIDE..WAVE HEIGHTS WILL DECREASE THIS
AFTERNOON ON WRN LK SUPERIOR..AND CURRENT EXPIRATION OF SMALL
CRAFT ADV ON THE NORTH SHORE AND SW TIP OF THE LAKE AT NOON AND
THE SOUTH SHORE LATER THIS AFTERNOON APPEAR REASONABLE.
MILLER
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR LSZ121-
LSZ146-LSZ147-LSZ148.
SMALL CRAFT ADVISORY UNTIL NOON CDT TODAY FOR LSZ140-LSZ141-
LSZ142-LSZ143-LSZ144-LSZ145.
&&
.PREV DISCUSSION... /ISSUED 757 AM CDT TUE APR 1 2008/
UPDATE...WE CANCELLED THE WINTER STORM WARNING THAT WAS STILL IN
EFFECT FOR ASHLAND AND IRON COUNTIES. SPOTTERS...WEBCAMS AND
OBSERVATIONS ALL INDICATE THE SNOW IS ENDING OR BECOMING LIGHT.
FLOW WAS STILL NORTHERLY OVER LAKE SUPERIOR WITH 850MB TEMPS
FORECAST TO BE AROUND -11C OR -12C...WHICH WOULD SUPPORT LAKE
EFFECT SNOW SHOWERS. HOWEVER...A TAMDAR SOUNDING NEAR CYQT HAD AN 850MB
TEMP A COUPLE DEGREES WARMER THAN THE MODELS FORECAST. WE DON`T
EXPECT MUCH FROM THE LAKE TODAY DUE TO THE DRIER AIR AND
SUBSIDENCE.
PREV DISCUSSION... /ISSUED 619 AM CDT TUE APR 1 2008/
UPDATE...EXTENDED WARNING A COUPLE HOURS ACROSS ASHLAND AND IRON
COUNTIES. STILL SOME SNOW BANDS WORKING THROUGH THAT AREA...WITH
SOME LAKE ENHANCEMENT LIKELY AS CAA CONTINUES EARLY THIS MORNING.
VSBYS AT KIWD CONTINUE TO BE 1 MILE OR LESS...AND SPOTTER AT GILE
REPORTED CONTINUED HEAVY SNOW AND CONSIDERABLE BLOWING AND
DRIFTING SNOW. SNOW AND WINDS SHOULD DIMINISH THERE THROUGH MID-
MORNING AS DRIER AIRMASS ADVECTS EASTWARD. REMAINDER OF WARNING
WAS ALLOWED TO EXPIRE...WITH JUST LIGHT SNOW EXPECTED NOW.
PREV DISCUSSION... /ISSUED 317 AM CDT TUE APR 1 2008/
DISCUSSION...EARLY MORNING SURFACE ANALYSIS DEPICTS LOW PRESSURE
CENTERED OVER NORTHERN LOWER MICHIGAN...WITH BACK DOOR TROUGH/COLD
FRONT PUSHING ACROSS NW WI. DEFORMATION AXIS OF SNOW HAS PIVOTED
AND IS NOW WEAKENING AND PULLING OFF TO THE EAST. LIGHT SNOW WITH
OCCASIONAL HEAVIER BANDS WILL CONTINUE THROUGH EARLY MORNING AS
SLOPING 2-D FGEN FORCING STILL EXISTS...SO WILL LEAVE WARNING
ENDING TIME AS SCHEDULED. ALSO...SOME EVIDENCE EXISTS FOR
DEVELOPING STANDING WAVE ALONG THE BAYFIELD PENINSULA AND SW TO
NORTHERN PINE COUNTY. SNOW TOTALS RECEIVED THROUGH THIS EARLY
MORNING GENERALLY RANGE FROM 4 TO 6 INCHES...WITH AN ISOLATED 11
INCH REPORT IN NORTHERN BAYFIELD COUNTY. SUSPECT THAT THERE WILL
BE MORE HIGH END REPORTS LATER THIS MORNING...ESPECIALLY ALONG
THE SOUTH SHORE WHERE VSBYS HAVE BEEN THE LOWEST OVERNIGHT.
LOW WILL EXIT QUICKLY THIS LATE MORNING...WITH CAA AND DRIER AIRMASS
BUILDING INTO THE REGION FROM THE WEST. HIGH PRESSURE UNDER WNW
FLOW ALOFT WILL REMAIN IN CONTROL THROUGH THIS EVENING. A WEAK
UPPER SHORT WAVE WILL PUSH THROUGH LATE TONIGHT AND WEDNESDAY.
SOME SNOW MAY DEVELOP ON THE NOSE OF 40+ KT LLJ AND WARM FRONT
PUSHING INTO NORTHERN MINNESOTA LATE TONIGHT AND WEDNESDAY
MORNING. BROADER LIFT ACROSS WAA ZONE WEDNESDAY AND WED NIGHT WILL
BRING THE CHANCE OF SOME LIGHT RAIN/SNOW...BUT OVERALL LIFT IS
WEAK AND MOISTURE IS LIMITED. OTHERWISE...A NICE WARMING TREND
LOOKS IN STORE FOR THE REMAINDER OF THE WEEK...WITH H85 TEMPS
APPROACHING 0C BY 00Z SAT...AND SFC TEMPS ABOVE NORMAL. LOOKING
AHEAD TO THIS SUNDAY...MODELS ARE ADVERTISING ANOTHER LOW
DEVELOPING OFF THE NORTHERN ROCKIES...BRINGING A CHANCE OF
RAIN/SNOW TO THE NORTHLAND.
AVIATION...LOW PRESSURE WILL CONTINUE TO PULL OFF TO THE EAST
TODAY...AND HIGH PRESSURE WILL BUILD INTO THE REGION. IFR/MVFR
CEILINGS AND VSBYS WERE MAINLY OVER NORTHWEST WISCONSIN EARLY THIS
MORNING...AND THEY WILL LIFT THROUGH THE DAY LEADING TO VFR
CONDITIONS. GUSTY WINDS EARLY WILL DIMINISH THROUGH THE DAY AS WELL
FROM WEST TO EAST ACROSS MINNESOTA AND WISCONSIN.
&&
POINT TEMPS/POPS...
DLH 35 17 42 26 / 10 10 20 20
INL 35 16 43 25 / 10 20 30 20
BRD 37 19 44 27 / 10 10 30 20
HYR 36 14 45 26 / 10 10 10 20
ASX 35 17 44 25 / 10 10 10 20
$$
AREA FORECAST DISCUSSION
NWS DULUTH MN
757 AM CDT TUE APR 1 2008
.UPDATE...WE CANCELLED THE WINTER STORM WARNING THAT WAS STILL IN
EFFECT FOR ASHLAND AND IRON COUNTIES. SPOTTERS...WEBCAMS AND
OBSERVATIONS ALL INDICATE THE SNOW IS ENDING OR BECOMING LIGHT.
FLOW WAS STILL NORTHERLY OVER LAKE SUPERIOR WITH 850MB TEMPS
FORECAST TO BE AROUND -11C OR -12C...WHICH WOULD SUPPORT LAKE
EFFECT SNOW SHOWERS. HOWEVER...A TAMDAR SOUNDING NEAR CYQT HAD AN 850MB
TEMP A COUPLE DEGREES WARMER THAN THE MODELS FORECAST. WE DON`T
EXPECT MUCH FROM THE LAKE TODAY DUE TO THE DRIER AIR AND
SUBSIDENCE.
&&
.PREV DISCUSSION... /ISSUED 619 AM CDT TUE APR 1 2008/
UPDATE...EXTENDED WARNING A COUPLE HOURS ACROSS ASHLAND AND IRON
COUNTIES. STILL SOME SNOW BANDS WORKING THROUGH THAT AREA...WITH
SOME LAKE ENHANCEMENT LIKELY AS CAA CONTINUES EARLY THIS MORNING.
VSBYS AT KIWD CONTINUE TO BE 1 MILE OR LESS...AND SPOTTER AT GILE
REPORTED CONTINUED HEAVY SNOW AND CONSIDERABLE BLOWING AND
DRIFTING SNOW. SNOW AND WINDS SHOULD DIMINISH THERE THROUGH MID-
MORNING AS DRIER AIRMASS ADVECTS EASTWARD. REMAINDER OF WARNING
WAS ALLOWED TO EXPIRE...WITH JUST LIGHT SNOW EXPECTED NOW.
PREV DISCUSSION... /ISSUED 317 AM CDT TUE APR 1 2008/
DISCUSSION...EARLY MORNING SURFACE ANALYSIS DEPICTS LOW PRESSURE
CENTERED OVER NORTHERN LOWER MICHIGAN...WITH BACK DOOR TROUGH/COLD
FRONT PUSHING ACROSS NW WI. DEFORMATION AXIS OF SNOW HAS PIVOTED
AND IS NOW WEAKENING AND PULLING OFF TO THE EAST. LIGHT SNOW WITH
OCCASIONAL HEAVIER BANDS WILL CONTINUE THROUGH EARLY MORNING AS
SLOPING 2-D FGEN FORCING STILL EXISTS...SO WILL LEAVE WARNING
ENDING TIME AS SCHEDULED. ALSO...SOME EVIDENCE EXISTS FOR
DEVELOPING STANDING WAVE ALONG THE BAYFIELD PENINSULA AND SW TO
NORTHERN PINE COUNTY. SNOW TOTALS RECEIVED THROUGH THIS EARLY
MORNING GENERALLY RANGE FROM 4 TO 6 INCHES...WITH AN ISOLATED 11
INCH REPORT IN NORTHERN BAYFIELD COUNTY. SUSPECT THAT THERE WILL
BE MORE HIGH END REPORTS LATER THIS MORNING...ESPECIALLY ALONG
THE SOUTH SHORE WHERE VSBYS HAVE BEEN THE LOWEST OVERNIGHT.
LOW WILL EXIT QUICKLY THIS LATE MORNING...WITH CAA AND DRIER AIRMASS
BUILDING INTO THE REGION FROM THE WEST. HIGH PRESSURE UNDER WNW
FLOW ALOFT WILL REMAIN IN CONTROL THROUGH THIS EVENING. A WEAK
UPPER SHORT WAVE WILL PUSH THROUGH LATE TONIGHT AND WEDNESDAY.
SOME SNOW MAY DEVELOP ON THE NOSE OF 40+ KT LLJ AND WARM FRONT
PUSHING INTO NORTHERN MINNESOTA LATE TONIGHT AND WEDNESDAY
MORNING. BROADER LIFT ACROSS WAA ZONE WEDNESDAY AND WED NIGHT WILL
BRING THE CHANCE OF SOME LIGHT RAIN/SNOW...BUT OVERALL LIFT IS
WEAK AND MOISTURE IS LIMITED. OTHERWISE...A NICE WARMING TREND
LOOKS IN STORE FOR THE REMAINDER OF THE WEEK...WITH H85 TEMPS
APPROACHING 0C BY 00Z SAT...AND SFC TEMPS ABOVE NORMAL. LOOKING
AHEAD TO THIS SUNDAY...MODELS ARE ADVERTISING ANOTHER LOW
DEVELOPING OFF THE NORTHERN ROCKIES...BRINGING A CHANCE OF
RAIN/SNOW TO THE NORTHLAND.
AVIATION...LOW PRESSURE WILL CONTINUE TO PULL OFF TO THE EAST
TODAY...AND HIGH PRESSURE WILL BUILD INTO THE REGION. IFR/MVFR
CEILINGS AND VSBYS WERE MAINLY OVER NORTHWEST WISCONSIN EARLY THIS
MORNING...AND THEY WILL LIFT THROUGH THE DAY LEADING TO VFR
CONDITIONS. GUSTY WINDS EARLY WILL DIMINISH THROUGH THE DAY AS WELL
FROM WEST TO EAST ACROSS MINNESOTA AND WISCONSIN.
&&
POINT TEMPS/POPS...
DLH 35 17 42 26 / 10 10 20 20
INL 37 16 43 25 / 10 20 30 20
BRD 38 19 44 27 / 10 10 30 20
HYR 38 14 45 26 / 40 10 10 20
ASX 35 17 44 25 / 60 10 10 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR LSZ121-
LSZ146-LSZ147-LSZ148.
SMALL CRAFT ADVISORY UNTIL NOON CDT TODAY FOR LSZ140-LSZ141-
LSZ142-LSZ143-LSZ144-LSZ145.
$$
MELDE/LILES
AREA FORECAST DISCUSSION
NWS RALEIGH NC
1007 AM EDT TUE APR 1 2008
.SYNOPSIS...BREEZY SOUTHERLY WINDS WILL SPREAD WARMER AIR OVER THE
REGION TODAY. A COLD FRONT WILL APPROACH FROM THE WEST TODAY AND
CROSS THE AREA TONIGHT. ANOTHER COOL HIGH PRESSURE AREA WILL BUILD
IN FROM THE NORTH ON WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1000 AM...
HAVE CUT BACK RAIN TO CHANCE CATEGORY. PRECIPITATION IMMEDIATELY
AHEAD OF THE FRONT IS WEAKENING AND CONTINUING THIS TREND. BEST
DYNAMICS FOR TODAY WILL BE IN THE EAST. AS TEMPERATURES WARM THIS
AFTERNOON THERE IS ENOUGH INSTABILITY FOR A RISK OF A
THUNDERSTORM ACROSS CENTRAL NORTH CAROLINA. SMALL HAIL CAN NOT BE
RULED OUT WITH FREEZING LEVELS BELOW 10000 FEET... WITH
POSSIBILITIES BETTER IN THE EAST.
BOUNDARY AS DEFINED BY DEWPOINTS BETWEEN RALEIGH AND GREENSBORO
WITH LOW 50S DEWPOINTS IN THE NORTHWEST. REAR EDGE OF THE UPPER
CLOUDS WILL MOVE THROUGH CENTRAL NORTH CAROLINA BY EARLY EVENING.
SURFACE FLOW BECOMES WEAKLY DIVERGENT. WITH SOUTHWEST FLOW ACROSS
THE AREA... EXPECTING THE BOUNDARY TO ERODE/LIFT OUT. SOME BRIEF
PEEKS AT THE SUN. HAVE MINIMALLY RAISED TEMPERATURES.
EXPECT GOOD MIXING THIS AFTERNOON. WITH WINDS IN EXCESS OF 25
KNOTS EXPECTED TO BE TAPPED...SOME GUSTINESS SHOULD DEVELOP LATE
MORNING INTO THE AFTERNOON.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
AS OF 320 AM TUESDAY...
SURFACE COLD FRONT STILL ON TRACK TO CROSS THE REGION LATE TONIGHT
THEN STALL NEAR OR JUST SOUTH OF THE REGION WEDNESDAY. COOL HIGH
PRESSURE OVER THE GREAT LAKES WILL TRANSLATE EAST INTO THE NORTHERN
MID ATLANTIC AND BUILD SOUTH INTO NC WED AND WED NIGHT. THIS
SCENARIO WILL SUPPORT ANOTHER COLD AIR DAMMING SITUATION (BUT SHOULD
NOT BE AS LONG IN DURATION AS RECENT EVENT). 925-850MB S-SW FLOW
WILL INCREASE LATE WED NIGHT INTO THU...INCREASING ISENTROPIC LIFT
FROM S-N ACROSS THE REGION. WILL BOOST POPS THU TO HIGH CHANCE (WILL
PROBABLY NEED TO INCREASE TO LIKELY OR LOW CATEGORICAL IN LATER
FORECAST ISSUANCES IF LATER MODEL GUIDANCE CONSISTENT). WITH
OVERCAST SKIES AND POTENTIAL FOR MORE RAIN...COOL TEMPS ANTICIPATED
FOR THU. WITH HYBRID DAMMING SET-UP...LOWERED MAX TEMPS A FEW
DEGREES IN THE NW PIEDMONT AND MAY NEED ADJUSTMENTS REMAINDER OF THE
PIEDMONT.
MODELS CURRENTLY IN GENERAL AGREEMENT ERODING CAD AIRMASS THU NIGHT
WITH MOIST WARM AIR MASS OVER THE REGION FRI INTO FRI NIGHT. EXPECT
TO SEE AN INCREASE IN SHOWERS FRI NIGHT INTO EARLY SATURDAY AS NEXT
COLD FRONT APPROACHES.
TEMPS WILL BE ON A ROLLER COASTER RIDE THIS WEEK. AFTER HIGHS TODAY
IN THE 60S/70S EXPECT A DOWNTURN WED INTO THU WITH MAX TEMPS WED
NEAR 60 NORTH TO MID 60S SOUTH..AND UPPER 40S NW TO LOWER 60S SE
THU. WARM SLY FLOW FRI WILL BOOST TEMPS BACK INTO THE 70S FRI.
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE LATEST 00Z/01 GFS IS BEGINNING TO TREND TOWARDS THE SLOWER
DETERMINISTIC SOLUTION OF THE ECMWF...INDICATING COLD FRONT PASSAGE
EXTENDING INTO THE AFTERNOON AND EVENING HOURS ON SATURDAY.
THE SLOWER TIMING IS ALSO IN BETTER AGREEMENT WITH THE GFS ENSEMBLE
MEAN. AS A RESULT...HAVE RAISED POPS TO CHANCE DURING THE DAY ON
SATURDAY...CONTINUING THE CHANCE OF SHOWERS AND THUNDERSTORMS...WITH
MODELS SHOWING A MODERATELY AMPLIFIED TROUGH ALOFT...FAVORABLE RR
JET DYNAMICS...AND STRONG DEEP (0 TO 6KM) LAYER SHEAR OF 45 TO
50KTS.
CLOUDS AND MOISTURE EXIT THE AREA OVERNIGHT SATURDAY NIGHT AS HIGH
PRESSURE BUILDS IN FROM THE WEST. UPPER FLOW REGIME LOOKS TO STAY
FLAT AND PROGRESSIVE INTO EARLY NEXT WEEK. SUNDAY AND MONDAY WILL
REMAIN DRY WITH SEASONABLE TEMPERATURES. HIGHS 65 TO 70. LOWS IN THE
40S.
&&
.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
AS OF 130 AM TUESDAY...
CLASSICAL DIABATICALLY ENHANCED COLD AIR DAMMING EVENT AND ASSOC
IFR/LIFR CONDITIONS CONTINUES ACROSS WESTERN PORTIONS OF THE
FORECAST AREA. LATEST OBSERVATION FROM THE RDU INTERNATIONAL REPORTS
2M SURFACE WINDS HAVE SWITCHED AROUND TO SOUTHERLY...INDICATING
WEDGE BOUNDARY(WARM FRONT)HAS JUST PUSHED WEST OF THE AREA. HARD TO
DETERMINE IF THIS IS PERMANENT...OR JUST TEMPORARILY...AS BOUNDARY
HAS BEEN MEANDERING WEST AND EAST OVER THE PAST EVENING.
EXPECT TO SEE IMPROVED IMPROVED CEILINGS/VISIBILITIES IN THE WARM SECTOR...EAST
OF THE TRIANGLE...WITH VISIBILITIES RANGING FROM MVFR TO VFR AND
CEILINGS RANGING FROM 200 TO 2000 FT...WITH LOWEST CONDITIONS
EXPECTED RIGHT ALONG THE FRONT AT THE RDU. IN THE WESTERN
PIEDMONT...WHERE WEDGE CONTINUES TO HANG TOUGH...LIFR TO IFR
CEILINGS AND VISIBILITIES. ALSO...AREA AMDAR AIRCRAFT SOUNDINGS
SHOW STRONG SOUTHERLY LOW LEVEL JET AND SHEAR OVER THE WEDGE REGIME...WITH 35
TO 40KTS AT OR ABOVE 1500FT...ATOP NEARLY CALM OR LIGHT NE WINDS. WILL
INCLUDE NON CONVECTIVE LOW LEVEL WIND SHEAR FOR JUST KINT AND KGSO THROUGH 12Z.
VISIBILITIES SHOULD REBOUND INTO THE VFR CATEGORY BY MIDDAY TUESDAY
(FROM EAST TO WEST) AS THE AIR NEAR THE SURFACE BECOMES WELL MIXED
(850 SOUTHWEST WINDS 45 TO 50 KTS) OUT AHEAD OF A COLD FRONT APPROACHING
FROM THE WEST. CEILINGS MAY BRIEFLY LIFT TO THE HIGH END OF MVFR OR
LOW END OF VFR BY TUESDAY AFTERNOON. HEATING OF THE MOIST AND
MARGINALLY UNSTABLE AIR MASS MAY LEAD TO THE DEVELOPMENT OF
SCATTERED SHOWERS OR THUNDERSTORMS TUESDAY AFTERNOON...ESPECIALLY
IN THE COASTAL PLAIN REGION. THESE SHOWERS/STORMS MAY PERSIST INTO
TUESDAY NIGHT AS A COLD FRONT CROSSES THE REGION. SOUTHWEST WINDS
WILL LIKELY BECOME BREEZY TUESDAY AFTERNOON AHEAD OF THE
FRONT...BECOMING SUSTAINED AT 10-15 KNOTS WITH GUSTS UP TO 25 KNOTS.
MAY SEE ANOTHER COLD AIR DAMMING EVENT WITH ASSOCIATED LOW
CEILINGS/VISIBILITIES WED NIGHT THROUGH THUR NIGHT AS ANOTHER STRONG
ARE OF HIGH PRESSURE BUILDS ACROSS THE NORTHERN MID ATLANTIC REGION.
ANOTHER COLD FRONT IS EXPECTED TO APPROACH FROM THE WEST FRIDAY
AFTERNOON...AND CROSS THE AREA EARLY SATURDAY. THIS COULD RESULT IN
MORE UNSETTLED WEATHER AT THAT TIME.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS RALEIGH NC
322 AM EDT TUE APR 1 2008
.SYNOPSIS...BREEZY SOUTHERLY WINDS WILL SPREAD WARMER AIR OVER THE
REGION TODAY. A COLD FRONT WILL APPROACH FROM THE WEST LATE TODAY
AND CROSS THE AREA TONIGHT. ANOTHER COOL HIGH PRESSURE AREA WILL
BUILD IN FROM THE NORTH ON WEDNESDAY.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 300 AM TUESDAY...
A SPLIT FLOW REGIME OVER THE WESTERN U.S THAT CONVERGES OVER THE
CENTRAL U.S. WILL MAINTAIN A UNSETTLED WEATHER PATTERN OVER CENTRAL
NC THROUGH THE NEXT 3-5 DAYS.
THIS MORNING...RESIDUAL PIEDMONT AIRMASS GRADUALLY ERODING OVER
THE WESTERN AND SOUTHERN PIEDMONT WHILE WARMER AIR MASS HAS
OVERSPREAD THE REMAINDER OF THE PIEDMONT INTO THE COASTAL PLAIN.
FOG MAINLY CONFINED TO AREAS UNDER THE INFLUENCE OF THE PIEDMONT
AIR MASS WHERE VISIBILITIES HOVERING BETWEEN 1/2-1SM. MAY
EVENTUALLY NEED A SHORT FUSE DENSE FOG ADVISORY FOR THE WESTERN
TIER OF COUNTIES.
ISENTROPIC LIFT IN THE 290-295K LAYER STILL PRODUCING WIDESPREAD
LIGHT RAIN/DRIZZLE ACROSS THE PIEDMONT. MODEL GUIDANCE INDICATE
THAT THIS WILL GRADUALLY WEAKEN BETWEEN 06-12Z TUE WITH MAIN LIFT
AT 12Z OVER THE COASTAL PLAIN. THUS WILL TAPER POPS AT 12Z FROM
CHANCE WEST TO LIKELY EAST.
THIS AFTERNOON...BREEZY S-SW LOW LEVEL FLOW WILL ADVECT MARGINALLY
UNSTABLE AIRMASS INTO THE REGION. MID LEVEL LAPSE RATES PROGGED TO
BE AROUND 6 DEG C AND LOW LEVEL WIND SHEAR PROFILE SUPPORTIVE OF
ORGANIZED CONVECTION. WET BULB ZERO HEIGHTS IN THE FAVORED RANGE
FOR LARGE HAIL. GFS SOUNDINGS MORE DIRER IN SEVERE POTENTIAL THAN
NAM BUT GFS ALSO SUGGEST SURFACE DEWPOINTS IN THE MID 60S (CHANCES
OF VERIFYING THIS SLIM). MAIN TRIGGER FOR SCATTERED TO NUMEROUS
SHOWERS AND A FEW STORMS WILL BE A FAST MOVING MID LEVEL TROUGH
SUPPORTED ALOFT BY AREA OF H3 DIFFLUENCE. DUE TO THE SOGGY AIRMASS
IN PLACE...LIKELY POPS WARRANTED FOR THIS AFTERNOON..AND INTO THE
EVENING IN THE EAST. WHILE WIDESPREAD SEVERE STORMS NOT
EXPECTED...THERE DOES APPEAR TO BE ENOUGH INSTABILITY AND
KINEMATICS TO SUPPORT ISOLATED SEVERE STORMS ACROSS THE
REGION...ESPECIALLY IN THE SANDHILLS AND THE COASTAL PLAIN. WILL
NEED TO MONITOR NEAR SURFACE DEWPOINTS. IF THESE START TO CREEP
INTO THE MID 60S...THINGS COULD BECOME INTERESTING IN A HURRY.
TEMPS TODAY STILL A BIT PROBLEMATIC IN THE NW PIEDMONT. WHILE
PIEDMONT AIRMASS RATHER SHALLOW...IT MAY TAKE A WHILE LONGER THAN
CURRENTLY FORECAST TO SCOUR OUT. MAX TEMPS IN THE UPPER 60S MAY BE
A STRETCH IN THE TRIAD AND MAY ADJUST DOWN A CATEGORY BEFORE
FORECAST ISSUANCE. OTHERWISE...BREEZY SLY FLOW WILL AID IN PUSHING
TEMPS ELSEWHERE ABOVE THE 70 DEGREE MARK (A NICE CHANGE AFTER THE
PAST FEW DAYS).
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
AS OF 320 AM TUESDAY...
SURFACE COLD FRONT STILL ON TRACK TO CROSS THE REGION LATE TONIGHT
THEN STALL NEAR OR JUST SOUTH OF THE REGION WEDNESDAY. COOL HIGH
PRESSURE OVER THE GREAT LAKES WILL TRANSLATE EAST INTO THE NORTHERN
MID ATLANTIC AND BUILD SOUTH INTO NC WED AND WED NIGHT. THIS
SCENARIO WILL SUPPORT ANOTHER COLD AIR DAMMING SITUATION (BUT SHOULD
NOT BE AS LONG IN DURATION AS RECENT EVENT). 925-850MB S-SW FLOW
WILL INCREASE LATE WED NIGHT INTO THU...INCREASING ISENTROPIC LIFT
FROM S-N ACROSS THE REGION. WILL BOOST POPS THU TO HIGH CHANCE (WILL
PROBABLY NEED TO INCREASE TO LIKELY OR LOW CATEGORICAL IN LATER
FORECAST ISSUANCES IF LATER MODEL GUIDANCE CONSISTENT). WITH
OVERCAST SKIES AND POTENTIAL FOR MORE RAIN...COOL TEMPS ANTICIPATED
FOR THU. WITH HYBRID DAMMING SET-UP...LOWERED MAX TEMPS A FEW
DEGREES IN THE NW PIEDMONT AND MAY NEED ADJUSTMENTS REMAINDER OF THE
PIEDMONT.
MODELS CURRENTLY IN GENERAL AGREEMENT ERODING CAD AIRMASS THU NIGHT
WITH MOIST WARM AIR MASS OVER THE REGION FRI INTO FRI NIGHT. EXPECT
TO SEE AN INCREASE IN SHOWERS FRI NIGHT INTO EARLY SATURDAY AS NEXT
COLD FRONT APPROACHES.
TEMPS WILL BE ON A ROLLER COASTER RIDE THIS WEEK. AFTER HIGHS TODAY
IN THE 60S/70S EXPECT A DOWNTURN WED INTO THU WITH MAX TEMPS WED
NEAR 60 NORTH TO MID 60S SOUTH..AND UPPER 40S NW TO LOWER 60S SE
THU. WARM SLY FLOW FRI WILL BOOST TEMPS BACK INTO THE 70S FRI.
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE LATEST 00Z/01 GFS IS BEGINNING TO TREND TOWARDS THE SLOWER
DETERMINISTIC SOLUTION OF THE ECMWF...INDICATING COLD FRONT PASSAGE
EXTENDING INTO THE AFTERNOON AND EVENING HOURS ON SATURDAY.
THE SLOWER TIMING IS ALSO IN BETTER AGREEMENT WITH THE GFSENSEMBLE
MEAN. AS A RESULT...HAVE RAISED POPS TO CHANCE DURING THE DAY ON
SATURDAY...CONTINUING THE CHANCE OF SHOWERS AND THUNDERSTORMS...WITH
MODELS SHOWING A MODERATELY AMPLIFIED TROUGH ALOFT...FAVORABLE RR
JET DYNAMICS...AND STRONG DEEP (0 TO 6KM) LAYER SHEAR OF 45 TO
50KTS.
CLOUDS AND MOISTURE EXIT THE AREA OVERNIGHT SATURDAY NIGHT AS HIGH
PRESSURE BUILDS IN FROM THE WEST. UPPER FLOW REGIME LOOKS TO STAY
FLAT AND PROGRESSIVE INTO EARLY NEXT WEEK. SUNDAY AND MONDAY WILL
REMAIN DRY WITH SEASONABLE TEMPERATURES. HIGHS 65 TO 70. LOWS IN THE
40S.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AS OF 130 AM TUESDAY...
CLASSICAL DIABATICALLY ENHANCED COLD AIR DAMMING EVENT AND ASSOC
IFR/LIFR CONDITIONS CONTINUES ACROSS WESTERN PORTIONS OF THE
FORECAST AREA. LATEST OBSERVATION FROM THE RDU INTERNATIONAL REPORTS
2M SURFACE WINDS HAVE SWITCHED AROUND TO SOUTHERLY...INDICATING
WEDGE BOUNDARY(WARM FRONT)HAS JUST PUSHED WEST OF THE AREA. HARD TO
DETERMINE IF THIS IS PERMANENT...OR JUST TEMPORARILY...AS BOUNDARY
HAS BEEN MEANDERING WEST AND EAST OVER THE PAST EVENING.
EXPECT TO SEE IMPROVED IMPROVED CIGS/VSBYS IN THE WARM SECTOR...EAST
OF THE TRIANGLE...WITH VISIBILITIES RANGING FROM MVFR TO VFR AND
CEILINGS RANGING FROM 200 TO 2000 FT...WITH LOWEST CONDITIONS
EXPECTED RIGHT ALONG THE FRONT AT THE RDU. IN THE WESTERN
PIEDMONT...WHERE WEDGE CONTINUES TO HANG TOUGH...LIFR TO IFR
CEILINGS AND VISIBILITIES. ALSO...AREA AMDAR AIRCRAFT SOUNDINGS
SHOW STRONG SOUTHERLY LLJ AND SHEAR OVER THE WEDGE REGIME...WITH 35
TO 40KTS AOA 1500FT...ATOP NEARLY CALM OR LIGHT NE WINDS. WILL
INCLUDE NON CONVECTIVE LLWS FOR JUST KINT AND KGSO THROUGH 12Z.
VISIBILITIES SHOULD REBOUND INTO THE VFR CATEGORY BY MIDDAY TUESDAY
(FROM EAST TO WEST) AS THE AIR NEAR THE SURFACE BECOMES WELL MIXED
(850 SWLY WINDS 45 TO 50 KTS) OUT AHEAD OF A COLD FRONT APPROACHING
FROM THE WEST. CEILINGS MAY BRIEFLY LIFT TO THE HIGH END OF MVFR OR
LOW END OF VFR BY TUESDAY AFTERNOON. HEATING OF THE MOIST AND
MARGINALLY UNSTABLE AIR MASS MAY LEAD TO THE DEVELOPMENT OF
SCATTERED SHOWERS OR THUNDERSTORMS TUESDAY AFTERNOON...ESPECIALLY
IN THE COASTAL PLAIN REGION. THESE SHOWERS/STORMS MAY PERSIST INTO
TUESDAY NIGHT AS A COLD FRONT CROSSES THE REGION. SOUTHWEST WINDS
WILL LIKELY BECOME BREEZY TUESDAY AFTERNOON AHEAD OF THE
FRONT...BECOMING SUSTAINED AT 10-15 KNOTS WITH GUSTS UP TO 25 KNOTS.
MAY SEE ANOTHER COLD AIR DAMMING EVENT WITH ASSOCIATED LOW
CEILINGS/VISIBILITIES WED NIGHT THROUGH THUR NIGHT AS ANOTHER STRONG
ARE OF HIGH PRESSURE BUILDS ACROSS THE NORTHERN MID ATLANTIC REGION.
ANOTHER COLD FRONT IS EXPECTED TO APPROACH FROM THE WEST FRIDAY
AFTERNOON...AND CROSS THE AREA EARLY SATURDAY. THIS COULD RESULT IN
MORE UNSETTLED WEATHER AT THAT TIME.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...CBL
AVIATION...CBL
AREA FORECAST DISCUSSION
NWS RALEIGH NC
305 AM EDT TUE APR 1 2008
.SYNOPSIS...BREEZY SOUTHERLY WINDS WILL SPREAD WARMER AIR OVER THE
REGION TODAY. A COLD FRONT WILL APPROACH FROM THE WEST LATE TODAY
AND CROSS THE AREA TONIGHT. ANOTHER COOL HIGH PRESSURE AREA WILL
BUILD IN FROM THE NORTH ON WEDNESDAY.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 300 AM TUESDAY...
A SPLIT FLOW REGIME OVER THE WESTERN U.S THAT CONVERGES OVER THE CENTRAL
U.S. WILL MAINTAIN A UNSETTLED WEATHER PATTERN OVER CENTRAL NC
THROUGH THE NEXT 3-5 DAYS.
THIS MORNING...RESIDUAL PIEDMONT AIRMASS GRADUALLY ERODING OVER
THE WESTERN AND SOUTHERN PIEDMONT WHILE WARMER AIR MASS HAS
OVERSPREAD THE REMAINDER OF THE PIEDMONT INTO THE COASTAL PLAIN.
FOG MAINLY CONFINED TO AREAS UNDER THE INFLUENCE OF THE PIEDMONT
AIR MASS WHERE VISIBILITIES HOVERING BETWEEN 1/2-1SM. MAY
EVENTUALLY NEED A SHORT FUSE DENSE FOG ADVISORY FOR THE WESTERN
TIER OF COUNTIES.
ISENTROPIC LIFT IN THE 290-295K LAYER STILL PRODUCING WIDESPREAD
LIGHT RAIN/DRIZZLE ACROSS THE PIEDMONT. MODEL GUIDANCE INDICATE
THAT THIS WILL GRADUALLY WEAKEN BETWEEN 06-12Z TUE WITH MAIN LIFT
AT 12Z OVER THE COASTAL PLAIN. THUS WILL TAPER POPS AT 12Z FROM
CHANCE WEST TO LIKELY EAST.
THIS AFTERNOON...BREEZY S-SW LOW LEVEL FLOW WILL ADVECT MARGINALLY
UNSTABLE AIRMASS INTO THE REGION. MID LEVEL LAPSE RATES PROGGED TO
BE AROUND 6 DEG C AND LOW LEVEL WIND SHEAR PROFILE SUPPORTIVE OF
ORGANIZED CONVECTION. WET BULB ZERO HEIGHTS IN THE FAVORED RANGE
FOR LARGE HAIL. GFS SOUNDINGS MORE DIRER IN SEVERE POTENTIAL THAN
NAM BUT GFS ALSO SUGGEST SURFACE DEWPOINTS IN THE MID 60S (CHANCES
OF VERIFYING THIS SLIM). MAIN TRIGGER FOR SCATTERED TO NUMEROUS
SHOWERS AND A FEW STORMS WILL BE A FAST MOVING MID LEVEL TROUGH
SUPPORTED ALOFT BY AREA OF H3 DIFFLUENCE. DUE TO THE SOGGY AIRMASS
IN PLACE...LIKELY POPS WARRANTED FOR THIS AFTERNOON..AND INTO THE
EVENING IN THE EAST. WHILE WIDESPREAD SEVERE STORMS NOT
EXPECTED...THERE DOES APPEAR TO BE ENOUGH INSTABILITY AND
KINEMATICS TO SUPPORT ISOLATED SEVERE STORMS ACROSS THE
REGION...ESPECIALLY IN THE SANDHILLS AND THE COASTAL PLAIN. WILL
NEED TO MONITOR NEAR SURFACE DEWPOINTS. IF THESE START TO CREEP
INTO THE MID 60S...THINGS COULD BECOME INTERESTING IN A HURRY.
TEMPS TODAY STILL A BIT PROBLEMATIC IN THE NW PIEDMONT. WHILE
PIEDMONT AIRMASS RATHER SHALLOW...IT MAY TAKE A WHILE LONGER THAN
CURRENTLY FORECAST TO SCOUR OUT. MAX TEMPS IN THE UPPER 60S MAY BE
A STRETCH IN THE TRIAD AND MAY ADJUST DOWN A CATEGORY BEFORE
FORECAST ISSUANCE. OTHERWISE...BREEZY SLY FLOW WILL AID IN PUSHING
TEMPS ELSEWHERE ABOVE THE 70 DEGREE MARK (A NICE CHANGE AFTER THE
PAST FEW DAYS).
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
AS OF 320 PM MONDAY...
WEAK REMNANTS OF THE WEDGE REGIME MAY STILL BE HOLDING ON IN THE
WINSTON-SALEM AREA AFTER SUNRISE TUESDAY... HOWEVER THIS SHOULD
QUICKLY ERODE AND THE REST OF THE AREA WILL BE FIRMLY IN THE WARM
SECTOR WITH STOUT SW FLOW AHEAD OF THE INCOMING COLD FRONT. FORCING
FOR ASCENT SHOULD BEGIN TO IMPROVE TUESDAY MORNING AS A WEAK MID
LEVEL PERTURBATION APPROACHES FROM THE WEST... BUT IN GENERAL THE
LIFT MECHANISMS SHOULD BE DECREASING AS ISENTROPIC UPGLIDE WANES AND
THE UPPER JET CORE HOLDS WELL TO OUR NORTH. FORECAST INSTABILITY IS
MARGINAL WITH MODEL CONSENSUS MUCAPE VALUES ONLY AROUND 400-800 J/KG
IN THE SOUTHEAST CWA... WHERE THE SREF PROBABILITY OF > 1000 J/KG OF
CAPE IS LESS THAN 20%. WIND FIELDS ARE DECENT THOUGH WITH 850 MB
WINDS SURPASSING 40 KTS. HAVE KEPT A MENTION OF THUNDER... MAINLY IN
THE SOUTHEAST HALF OF THE AREA... BUT THE OVERALL RISK OF MORE THAN
A COUPLE OF STRONG STORMS IS SMALL AND THREATS SHOULD BE LIMITED TO
STRONG GUSTS. WILL HAVE HIGHS 69-75... REASONABLE CONSIDERING
THICKNESSES ARE PROJECTED TO BE AROUND 30 M ABOVE NORMAL.
THE COLD FRONT IS EXPECTED TO DROP SOUTHEASTWARD INTO THE NW
PIEDMONT TUESDAY EVENING AND BE ORIENTED ACROSS THE SOUTHEAST CWA
WEDNESDAY MORNING. HAVE KEPT CHANCE POPS FOR SHOWERS THROUGH TUESDAY
NIGHT INTO WEDNESDAY MORNING... WITH FORCING LIMITED TO FRONTAL MASS
CONVERGENCE. A CHILLY 1035 MB HIGH WILL PUSH IN FROM THE GREAT LAKES
IN WHAT LOOKS TO BE ANOTHER DEVELOPING COLD AIR DAMMING EVENT. THIS
HIGH SHOULD BE SOMEWHAT MODIFIED AS IT ARRIVES BUT WITH VERY COLD
TEMPERATURES AND DEWPOINTS CURRENTLY BENEATH IT... IT SHOULD PACK
ENOUGH OF A PUNCH OF COLD AIR TO HOLD HIGHS WEDNESDAY IN THE 60-65
DEGREE RANGE... AFTER LOWS OF 50-58. -GIH
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 AM MONDAY...
THE LATEST 00Z/01 GFS IS BEGINNING TO TREND TOWARDS THE SLOWER
DETERMINISTIC SOLUTION OF THE ECMWF...INDICATING COLD FRONT PASSAGE
EXTENDING INTO THE AFTERNOON AND EVENING HOURS ON SATURDAY.
THE SLOWER TIMING IS ALSO IN BETTER AGREEMENT WITH THE GFSENSEMBLE
MEAN. AS A RESULT...HAVE RAISED POPS TO CHANCE DURING THE DAY ON
SATURDAY...CONTINUING THE CHANCE OF SHOWERS AND THUNDERSTORMS...WITH
MODELS SHOWING A MODERATELY AMPLIFIED TROUGH ALOFT...FAVORABLE RR
JET DYNAMICS...AND STRONG DEEP (0 TO 6KM) LAYER SHEAR OF 45 TO
50KTS.
CLOUDS AND MOISTURE EXIT THE AREA OVERNIGHT SATURDAY NIGHT AS HIGH
PRESSURE BUILDS IN FROM THE WEST. UPPER FLOW REGIME LOOKS TO STAY
FLAT AND PROGRESSIVE INTO EARLY NEXT WEEK. SUNDAY AND MONDAY WILL
REMAIN DRY WITH SEASONABLE TEMPERATURES. HIGHS 65 TO 70. LOWS IN THE
40S.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AS OF 130 AM TUESDAY...
CLASSICAL DIABATICALLY ENHANCED COLD AIR DAMMING EVENT AND ASSOC
IFR/LIFR CONDITIONS CONTINUES ACROSS WESTERN PORTIONS OF THE
FORECAST AREA. LATEST OBSERVATION FROM THE RDU INTERNATIONAL REPORTS
2M SURFACE WINDS HAVE SWITCHED AROUND TO SOUTHERLY...INDICATING
WEDGE BOUNDARY(WARM FRONT)HAS JUST PUSHED WEST OF THE AREA. HARD TO
DETERMINE IF THIS IS PERMANENT...OR JUST TEMPORARILY...AS BOUNDARY
HAS BEEN MEANDERING WEST AND EAST OVER THE PAST EVENING.
EXPECT TO SEE IMPROVED IMPROVED CIGS/VSBYS IN THE WARM SECTOR...EAST
OF THE TRIANGLE...WITH VISIBILITIES RANGING FROM MVFR TO VFR AND
CEILINGS RANGING FROM 200 TO 2000 FT...WITH LOWEST CONDITIONS
EXPECTED RIGHT ALONG THE FRONT AT THE RDU. IN THE WESTERN
PIEDMONT...WHERE WEDGE CONTINUES TO HANG TOUGH...LIFR TO IFR
CEILIINGS AND VISIBILITIES. ALSO...AREA AMDAR AIRCRAFT SOUNDINGS
SHOW STRONG SOUTHERLY LLJ AND SHEAR OVER THE WEDGE REGIME...WITH 35
TO 40KTS AOA 1500FT...ATOP NEARLY CALM OR LIGHT NE WINDS. WILL
INCLUDE NON CONVECTIVE LLWS FOR JUST KINT AND KGSO THROUGH 12Z.
VISIBILITIES SHOULD REBOUND INTO THE VFR CATEGORY BY MIDDAY TUESDAY
(FROM EAST TO WEST) AS THE AIR NEAR THE SURFACE BECOMES WELL MIXED
(850 SWLY WINDS 45 TO 50 KTS) OUT AHEAD OF A COLD FRONT APPROACHING
FROM THE WEST. CEILINGS MAY BRIEFLY LIFT TO THE HIGH END OF MVFR OR
LOW END OF VFR BY TUESDAY AFTERNOON. HEATING OF THE MOIST AND
MARGINALLY UNSTABLE AIR MASS MAY LEAD TO THE DEVELOPMENT OF
SCATTERED SHOWERS OR THUNDERSTORMS TUESDAY AFTERNOON...ESPECIALLY
IN THE COASTAL PLAIN REGION. THESE SHOWERS/STORMS MAY PERSIST INTO
TUESDAY NIGHT AS A COLD FRONT CROSSES THE REGION. SOUTHWEST WINDS
WILL LIKELY BECOME BREEZY TUESDAY AFTERNOON AHEAD OF THE
FRONT...BECOMING SUSTAINED AT 10-15 KNOTS WITH GUSTS UP TO 25 KNOTS.
MAY SEE ANOTHER COLD AIR DAMMING EVENT WITH ASSOCIATED LOW
CEILINGS/VISIBILITIES WED NIGHT THROUGH THUR NIGHT AS ANOTHER STRONG
ARE OF HIGH PRESSURE BUILDS ACROSS THE NORTHERN MID ATLANTIC REGION.
ANOTHER COLD FRONT IS EXPECTED TO APPROACH FROM THE WEST FRIDAY
AFTERNOON...AND CROSS THE AREA EARLY SATURDAY. THIS COULD RESULT IN
MORE UNSETTLED WEATHER AT THAT TIME.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...CBL
AVIATION...CBL
AREA FORECAST DISCUSSION
NWS RALEIGH NC
130 AM EDT TUE APR 01 2008
.SYNOPSIS...
A STATIONARY FRONT WILL LINGER OVER CENTRAL NC TONIGHT THEN MOVE
NORTHWEST AS A WARM FRONT TUE. A COLD FRONT WILL APPROACH FROM THE
WEST LATE TUESDAY AND CROSS THE AREA TUESDAY NIGHT. ANOTHER COOL
HIGH PRESSURE AREA WILL BUILD IN FROM THE NORTH ON WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
AS OF 720 PM MONDAY...
THE NEARLY STATIONARY FRONT IS EXPECTED TO REMAIN OVER THE EASTERN
PIEDMONT AND SANDHILLS OVERNIGHT WITH CONVERGENCE OF WARM HUMID AIR
ON SOUTHERLY FLOW IN VICINITY OF THE FRONT NEAR THE SURFACE. THIS
WILL MAINTAIN A STEADY FEED OF RAIN AREAS FROM COASTAL SC INTO THE
RAH CWA DURING THE NIGHT WITH THE GREATEST AMOUNTS ALONG THE U.S.
ROUTE ONE CORRIDOR. THE SATURATED LOW LEVEL AIR AND WEAK SURFACE
FLOW IN THE COOL POOL WEST OF THE FRONT SHOULD LEAD TO WIDESPREAD
FOG...POSSIBLY DENSE TOWARD MORNING. TEMPERATURES WILL SHOW ONLY
MINOR FALLS EAST AND STEADY TO SLIGHTLY RISING OVERNIGHT WEST. -RFG
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
AS OF 320 PM MONDAY...
WEAK REMNANTS OF THE WEDGE REGIME MAY STILL BE HOLDING ON IN THE
WINSTON-SALEM AREA AFTER SUNRISE TUESDAY... HOWEVER THIS SHOULD
QUICKLY ERODE AND THE REST OF THE AREA WILL BE FIRMLY IN THE WARM
SECTOR WITH STOUT SW FLOW AHEAD OF THE INCOMING COLD FRONT. FORCING
FOR ASCENT SHOULD BEGIN TO IMPROVE TUESDAY MORNING AS A WEAK MID
LEVEL PERTURBATION APPROACHES FROM THE WEST... BUT IN GENERAL THE
LIFT MECHANISMS SHOULD BE DECREASING AS ISENTROPIC UPGLIDE WANES AND
THE UPPER JET CORE HOLDS WELL TO OUR NORTH. FORECAST INSTABILITY IS
MARGINAL WITH MODEL CONSENSUS MUCAPE VALUES ONLY AROUND 400-800 J/KG
IN THE SOUTHEAST CWA... WHERE THE SREF PROBABILITY OF > 1000 J/KG OF
CAPE IS LESS THAN 20%. WIND FIELDS ARE DECENT THOUGH WITH 850 MB
WINDS SURPASSING 40 KTS. HAVE KEPT A MENTION OF THUNDER... MAINLY IN
THE SOUTHEAST HALF OF THE AREA... BUT THE OVERALL RISK OF MORE THAN
A COUPLE OF STRONG STORMS IS SMALL AND THREATS SHOULD BE LIMITED TO
STRONG GUSTS. WILL HAVE HIGHS 69-75... REASONABLE CONSIDERING
THICKNESSES ARE PROJECTED TO BE AROUND 30 M ABOVE NORMAL.
THE COLD FRONT IS EXPECTED TO DROP SOUTHEASTWARD INTO THE NW
PIEDMONT TUESDAY EVENING AND BE ORIENTED ACROSS THE SOUTHEAST CWA
WEDNESDAY MORNING. HAVE KEPT CHANCE POPS FOR SHOWERS THROUGH TUESDAY
NIGHT INTO WEDNESDAY MORNING... WITH FORCING LIMITED TO FRONTAL MASS
CONVERGENCE. A CHILLY 1035 MB HIGH WILL PUSH IN FROM THE GREAT LAKES
IN WHAT LOOKS TO BE ANOTHER DEVELOPING COLD AIR DAMMING EVENT. THIS
HIGH SHOULD BE SOMEWHAT MODIFIED AS IT ARRIVES BUT WITH VERY COLD
TEMPERATURES AND DEWPOINTS CURRENTLY BENEATH IT... IT SHOULD PACK
ENOUGH OF A PUNCH OF COLD AIR TO HOLD HIGHS WEDNESDAY IN THE 60-65
DEGREE RANGE... AFTER LOWS OF 50-58. -GIH
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
AS OF 145 PM MONDAY...
FORECAST CONFIDENCE CONTINUES TO INCREASE FOR THE THU-THU NIGHT
PERIOD. A FRESH... INITIALLY DRY CLASSICAL COLD AIR DAMMING HIGH
(1030 TO 1035 MB) WILL BUILD EASTWARD FROM THE EASTERN GREAT LAKES
REGION WEDNESDAY EVENING REGION TO THE JERSEY COAST BY THURSDAY
MORNING. FORECAST LOW LEVEL THICKNESSES DIP B/W 1320 AND 1340
METERS... WITH DRY SFC DEWPOINTS IN THE 25 TO 35 DEGREE RANGE BY
12Z THU. THIS WILL SET THE STAGE FOR ALMOST A MIRROR IMAGE OF
TODAY... WITH STRONG ISENTROPIC LIFT (30 KT CROSS CONTOUR/TIGHT
GRADIENT FLOW) IN THE 290-300 K LAYER AND ATOP THE SFC WEDGE...
AND RESULT IN ANOTHER CLASSICAL DIABATICALLY ENHANCED CAD EVENT
THURSDAY AND THURSDAY NIGHT. WILL ACCORDINGLY SHOW AN INCREASING
CHANCE OF RAIN BEGINNING THURSDAY MORNING IN THE SOUTH AND EARLY
AFTERNOON NORTH... CONTINUING THROUGH THE NIGHTTIME HOURS. HIGHS
WILL STRUGGLE TO REACH 50 IN THE TRIAD... WITH LOWER 60S IN THE
COASTAL PLAIN... EAST OF THE RETREATING CAD FRONT FROM THE COAST.
FRI-FRI NIGHT...THE MEDIUM RANGE GUIDANCE IS STILL IN DISAGREEMENT
REGARDING THE EVOLUTION OF THE UPPER TROUGH CURRENTLY NEAR 140W/35N
IN THE EASTERN PACIFIC. THE LAST FEW CYCLES OF GFS QUICKLY ADVANCE
THIS FEATURE ACROSS THE CONUS AND PLACES AN ATTENDANT SFC WAVE IN
THE OHIO VALLEY AT 12Z FRI. THE LAST 2 ECMWF CYCLES... ON THE OTHER
HAND... ARE MUCH SLOWER WITH THE PROGRESSION OF THE UPPER TROUGH AND
ACCORDINGLY HOLD THE SFC WAVE OVER THE SOUTHERN PLAINS AT THAT TIME.
GIVEN THE CONTINUED UNCERTAINTY... WILL CLOSELY FOLLOW HPC WITH
SOMEWHAT OF A BLEND OF THESE TWO SOLUTIONS... WHICH WOULD RESULT IN
THE SFC LOW ADVANCING THROUGH THE TN VALLEY FRIDAY... WITH AN
ATTENDANT COLD FRONTAL PASSAGE THROUGH NC SATURDAY MORNING. THE
PASSAGE OF THE LOW THROUGH THE TN VALLEY FRIDAY IS A CAD EROSION
SCENARIO WHICH SHOULD LEAD TO THE DEMISE OF THE RESIDUAL CAD WEDGE
FROM THURSDAY NIGHT. INCREASING SOUTHWESTERLY FLOW AHEAD OF THE LOW
SHOULD BOOST HIGHS INTO THE 70S ACROSS THE FORECAST AREA... PERHAPS
NEARING 80 IN THE COASTAL PLAIN. THERMAL PROFILES BECOME SUPPORTIVE
OF DEEP CONVECTION FRIDAY AFTERNOON... BUT A LACK OF ANY DISCERNIBLE
TRIGGER MAY PRECLUDE DEVELOPMENT UNTIL THE FRONT DRAWS NEARER LATER
FRIDAY EVENING INTO THE OVERNIGHT.
FORECAST CONFIDENCE FURTHER DECREASES THROUGH THE WEEKEND...AS THE
GFS STALLS THE SFC FRONT JUST TO OUR SOUTH... WHERE IT INDUCES
CYCLOGENESIS THAT RUNS UP THE COAST SATURDAY AND SATURDAY NIGHT.
THIS IS A RESULT OF ANOTHER PROGRESSIVE TROUGH ALOFT WHOSE EVOLUTION
THE MODELS DO NOT AGREE ON. WILL ACCORDINGLY STICK NEAR CLIMO IN THE
SATURDAY THROUGH MONDAY TIME FRAME... AND MAINTAIN SILENT CHANCE
POP. -MWS
&&
.AVIATION /00Z MONDAY THROUGH SATURDAY/...
AS OF 130 AM TUESDAY...
CLASSICAL DIABATICALLY ENHANCED COLD AIR DAMMING EVENT AND ASSOC
IFR/LIFR CONDITIONS CONTINUES ACROSS WESTERN PORTIONS OF THE
FORECAST AREA. LATEST OBSERVATION FROM THE RDU INTERNATIONAL REPORTS
2M SURFACE WINDS HAVE SWITCHED AROUND TO SOUTHERLY...INDICATING
WEDGE BOUNDARY(WARM FRONT)HAS JUST PUSHED WEST OF THE AREA. HARD TO
DETERMINE IF THIS IS PERMANENT...OR JUST TEMPORARILY...AS BOUNDARY
HAS BEEN MEANDERING WEST AND EAST OVER THE PAST EVENING.
EXPECT TO SEE IMPROVED IMPROVED CIGS/VSBYS IN THE WARM SECTOR...EAST
OF THE TRIANGLE...WITH VISIBILITIES RANGING FROM MVFR TO VFR AND
CEILINGS RANGING FROM 200 TO 2000 FT...WITH LOWEST CONDITIONS
EXPECTED RIGHT ALONG THE FRONT AT THE RDU. IN THE WESTERN
PIEDMONT...WHERE WEDGE CONTINUES TO HANG TOUGH...LIFR TO IFR
CEILIINGS AND VISIBILITIES. ALSO...AREA AMDAR AIRCRAFT SOUNDINGS
SHOW STRONG SOUTHERLY LLJ AND SHEAR OVER THE WEDGE REGIME...WITH 35
TO 40KTS AOA 1500FT...ATOP NEARLY CALM OR LIGHT NE WINDS. WILL
INCLUDE NON CONVECTIVE LLWS FOR JUST KINT AND KGSO THROUGH 12Z.
VISIBILITIES SHOULD REBOUND INTO THE VFR CATEGORY BY MIDDAY TUESDAY
(FROM EAST TO WEST) AS THE AIR NEAR THE SURFACE BECOMES WELL MIXED
(850 SWLY WINDS 45 TO 50 KTS) OUT AHEAD OF A COLD FRONT APPROACHING
FROM THE WEST. CEILINGS MAY BRIEFLY LIFT TO THE HIGH END OF MVFR OR
LOW END OF VFR BY TUESDAY AFTERNOON. HEATING OF THE MOIST AND
MARGINALLY UNSTABLE AIR MASS MAY LEAD TO THE DEVELOPMENT OF
SCATTERED SHOWERS OR THUNDERSTORMS TUESDAY AFTERNOON...ESPECIALLY
IN THE COASTAL PLAIN REGION. THESE SHOWERS/STORMS MAY PERSIST INTO
TUESDAY NIGHT AS A COLD FRONT CROSSES THE REGION. SOUTHWEST WINDS
WILL LIKELY BECOME BREEZY TUESDAY AFTERNOON AHEAD OF THE
FRONT...BECOMING SUSTAINED AT 10-15 KNOTS WITH GUSTS UP TO 25 KNOTS.
MAY SEE ANOTHER COLD AIR DAMMING EVENT WITH ASSOCIATED LOW
CEILINGS/VISIBILITIES WED NIGHT THROUGH THUR NIGHT AS ANOTHER STRONG
ARE OF HIGH PRESSURE BUILDS ACROSS THE NORTHERN MID ATLANTIC REGION.
ANOTHER COLD FRONT IS EXPECTED TO APPROACH FROM THE WEST FRIDAY
AFTERNOON...AND CROSS THE AREA EARLY SATURDAY. THIS COULD RESULT IN
MORE UNSETTLED WEATHER AT THAT TIME.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...RFG
NEAR TERM...RFG
SHORT TERM...HARTFIELD
LONG TERM...MWS
AVIATION...CBL/VINCENT
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
101 PM CDT WED APR 2 2008
.AVIATION...
THE WEAK FRONT WAS HEADING SLOWLY BACK NORTHWARD EARLY THIS
AFTERNOON. AREAS OF LIGHT FOG AND DRIZZLE WERE ACCOMPANIED BY A
LINE OF SHOWERS ALONG THE FRONT. THESE SHOULD IMPACT THE TERMINAL
SITES FROM HOU NORTHWARD TO UTS. A FEW BREAKS IN THE MVFR CEILINGS
MAY OCCUR THROUGH THE MID AND LATE AFTERNOON PERIOD. BY LATE
EVENING MVFR CONDITIONS WILL REDEVELOP AS THE LOW-LEVEL JET GETS
ESTABLISHED. IFR CONDITIONS ARE EXPECTED TO DEVELOP BETWEEN 06Z
AND 10Z. DURING THE LAST 6 HOURS OF THE FORECAST...BREEZY
CONDITIONS WILL DEVELOP AS THE CEILINGS BEGIN TO LIFT AND THE LOW-
LEVEL INVERSION BREAKS.
40
&&
.PREV DISCUSSION... /ISSUED 946 AM CDT WED APR 2 2008/
DISCUSSION...
DIFFUSE FRONTAL BOUNDARY SITTING ACROSS SRN PARTS OF THE AREA
SHOULD HEAD BACK NORTH AS A WARM FRONT LATER TODAY. MORNING
SOUNDINGS AND AIRCRAFT SOUNDINGS INDICATE A NOTICEABLE CAP THAT
SHOULD BE PRETTY TOUGH TO OVERCOME. WOULD NEED TO WARM TO 84+ FOR
THIS TO OCCUR. THINK ISOLATED POPS ALREADY IN THE FCST SHOULD
COVER THAT WELL. TEMPS ALSO LOOK GOOD. TWEAKED THE CLOUD COVER &
WINDS IN THE GRIDDED DATA BASED ON LATEST CONDITIONS/OBS. DON`T
THINK IT`LL RESULT IN MANY CHANGES IN THE TEXT PRODUCTS BUT WILL
GO AHEAD AND RUN THEM AND SHIP THEM OUT ANYWAYS. 47
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 78 67 80 63 72 / 20 10 10 40 40
HOUSTON (IAH) 81 67 82 66 74 / 20 10 10 20 50
GALVESTON (GLS) 78 69 77 68 76 / 20 10 10 10 50
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
DISCUSSION...47
AVIATION/MARINE...40
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
348 AM CDT TUE APR 1 2008
FORECAST FOCUS ON ENDING PRECIPITATION THIS MORNING...WINDS
TODAY...AND PRECIPITATION CHANCES THURSDAY THROUGH FRIDAY.
LATEST WATER VAPOR IMAGERY INDICATED A SHORTWAVE TROUGH EXTENDING
FROM NORTHEAST MINNESOTA SOUTHWEST INTO NORTHEAST NEBRASKA.
VORTICITY MAXIMUM WITHIN THIS TROUGH WAS DRIVING CURRENT SNOW
ACTIVITY OVER SOUTHERN MINNESOTA INTO CENTRAL WISCONSIN.
AT THE SURFACE...LOW PRESSURE MOVING INTO NORTHERN LOWER MICHIGAN
PULLED ITS COLD FRONT THROUGH SOUTHERN WISCONSIN. TEMPERATURES
QUICKLY FELL INTO THE 30S BEHIND THE FRONT.
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...
FIRST ISSUE IS TIMING OUT LINGERING SNOW SHOWERS THIS MORNING.
AREA FORECAST SOUNDINGS SHOWED MOIST LOW LEVEL LAYER GRADUALLY
RISING DURING THE MORNING HOURS...WITH RELATIVELY STEEP LOW LEVEL
LAPSE RATES. LOCAL HIGH RESOLUTION 4KM MODELS KEPT MOST OF THE
SNOW JUST NORTH OF THE FORECAST AREA.
HOWEVER...GIVEN CURRENT SOUTHEAST MOVEMENT OF SNOW SHOWERS...COULD
SEE SOME ACTIVITY MAKE IT INTO THE FORECAST AREA BEFORE SHORTWAVE
TROUGH MOVES THROUGH THE REGION. WILL GO WITH SCATTERED SNOW
SHOWER OR FLURRY WORDING IN NORTHEAST 2/3 OF FORECAST AREA. ANY
SNOW ACCUMULATIONS WOULD BE LIGHT.
NEXT ISSUE IS WINDY CONDITIONS FOR TODAY. STRONG COLD AIR
ADVECTION CONTINUES TODAY...WITH 1000/500MB THICKNESSES DROPPING
FROM THE 530S DKM RANGE AT 12Z TUESDAY TO THE LOWER 520S DKM RANGE
BY 00Z WEDNESDAY. SURFACE PRESSURE GRADIENT STRONGEST THIS
MORNING...BEFORE GRADUALLY EASING BY EVENING.
AREA FORECAST SOUNDINGS SHOWED GOOD MIXING POTENTIAL UP TO 6000
FEET. WIND GUSTS IN THE 25 TO 35 KNOT RANGE IN THE MIXING LAYER
ARE POSSIBLE. MAY SEE AN ISOLATED GUST OR SUSTAINED WIND TO WIND
ADVISORY CRITERIA...BUT DO NOT EXPECT WIDESPREAD ACTIVITY.
SO...WILL HOLD OFF ON A WIND ADVISORY AND JUST MENTION BRISK/WINDY
WORDING IN FORECAST.
HIGH PRESSURE MOVING ACROSS THE REGION SHOULD BRING QUIET WEATHER
TONIGHT THROUGH WEDNESDAY NIGHT.
.LONG TERM...THURSDAY THROUGH MONDAY...
MODELS WERE KEEPING MOST OF THE PRECIPITATION ASSOCIATED WITH THE
NEXT LOW PRESSURE SYSTEM SOUTH OF WISCONSIN FOR THURSDAY THROUGH
FRIDAY. GFS ENSEMBLES FOLLOW THIS TREND WITH THEIR MEAN QPF
FIELDS...WHILE THE ECMWF AND GFS HAVE VERY LIGHT QPF UP TO THE
WISCONSIN AND ILLINOIS BORDER. HPC HAD BELOW AVERAGE CONFIDENCE IN
THIS PERIOD WITH THE MEDIUM RANGE MODELS. WILL JUST MENTION A
SLIGHT CHANCE FOR THURSDAY AND THURSDAY NIGHT IN SOUTHERN PORTIONS
OF THE AREA.
AFTER THAT...MODELS DIVERGE ON SYSTEM FOR THE WEEKEND. WILL LEAVE
THIS PERIOD AS IS FOR NOW.
&&
.AVIATION...EXPECT PATCHY DRIZZLE TO DIMINISH/END FOR A TIME
BEFORE SCATTERED SNOW SHOWERS/FLURRIES SWEEPS THROUGH THIS MORNING
IN RESPONSE TO PASSING MID LEVEL SHORT WAVE TROUGH. IFR CIGS
SHOULD IMPROVE TO MVFR THIS MRNG AND VFR THIS AFTERNOON AS
SUBSIDENCE DRYING MIXES WITH IN FROM THE NORTHWEST. WIDESPREAD
CLEARING AFT 22Z.
&&
.MARINE...LATEST TAMDAR SOUNDINGS OVER CENTRAL WI VERIFYING
STRONGER LOW LEVEL WINDS ASSOCIATED WITH NAM. HENCE WILL FOLLOW
NAM GUIDANCE OVER THE NEARSHORE WHICH SHOWS STEEP LAPSE RATES NEAR
DRY ADIABATIC...DEVELOPING THIS MORNING. STEEP LAPSE RATES
EXPECTED TO REACH 870MB WHICH WILL ALLOW WIND GUSTS TO 35KTS REACH
LAKE SURFACE. GUST TO 40KTS OVER SOUTHERN PORTION OF GREEN BAY
EARLIER. HENCE WL CONVERT SMALL CRAFT TO GALE WARNING AND RUN IT
INTO THE EARLY AFTN. CAN THEN DOWNGRADE TO SMALL CRAFT INTO EARLY
EVE.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...GALE WARNING UNTIL 4 PM CDT THIS AFTERNOON FOR LMZ643>646.
&&
$$
SHORT/LONG TERM...08/WOOD
AVIATION/MARINE...11/MBK
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